While most answers either use a simple proportion or shift-off to alternate biology, I'll focus on lifespan problem. So, my answer is not specific to elves, it's about longer-living (and probably genetically engineered) people.
The problem with the proportion is that you would assume the phases of life to take the same share of one's life, but longer since the whole life is longer. Meaning that if it takes 18 years to get mature now, it would take like 40 years, if we would live for, like, 200 years. (Folks in their teens were regarded adults in earlier history.) One real reason (beyond proportion) for such tendency would be a prolonged education. You need to learn until you are 40 to be a proper and productive member of that society.
The current tendency with human populace is less prolonged adolescence (even despite my above reference to the Dark Ages), but more the prolonged geriatrics. While adolescence and active adult life (such as working age up to retirement) stay relatively the same (see the enhancement of the retirement age as the recent trend in various counties though), the time left after retirement enhanced vastly. Like, people previously retired with 60 and were sort-of-expected to die at 65-75. Now they retire at 65 and can well live beyond 90.
So my point is that when scaling up the life expectancy to elvish, you are better off when you don't blindly scale up things, but set two ages, the maturity and the retirement, and then play accordingly.
Let's take the life expectancy of 200 years, more than doubling the human life span. It seems reasonable to extend the adolescence to 25 years at least.
(Notice that if your elvish (other biology!) populace has not gone though industrial revolution, antibiotica boom, and progress in public healthcare, that would severely extend the life span from the natural figures – basically, if they have always lived for 200 years, then the physiology of an elf is also different. This was the long way to say that they don't hit the puberty at 13-14. Make it 18-20.)
Now, while in humans the typical retirement age is somewhat above becoming grand parents (it's possible to become a granny with 40, while 50-60 is more reasonable), we don't know how it works in elves. The linear scaling of a proportion would have saved us from this, providing for longer generations in elves. If we assume somewhat human behaviour, even is stretched-up a bit, it seems reasonable for our elves to typically have kids at 40-50-60. (Of course, they can get pregnant at 20, but so can human teenagers.)
This means that we have elvish grandparents at 100 and grand-grandparents at 150. 3/4 of the life span (150 in elves) seems like a lot (75 in 100-year-lifespan humans), but it's 60 in 80-year-lifespan humans. Around this seems to be a perfect age for retirement. Making adjustments for ageing populace and what not (similar to what governments of developed countries tell us, when they bump retirement age), let's set the retirement age at 160. This leaves you with enough time to travel the world. Like, to visit the elvish Paris and snip an elvish pic of them in front of elvish Eiffel tower.
Provided system has a few major consequences.
It was typical for longer in human society that grandparents provide help to parents, especially if the latter a young and working. Elvish grandparents would have not retired yet! They are in their primes! So, either grand-grandparents need to jump in, or the grandparents need to take some kind of a sabbatical. Other systems might be in place, it is a given to hire grannies, or elvish children are not that care-intensive (remember, different biology!). It might be that elvish grand-grandparents don't give a damn about their grandchildren, preferring to travel the elvish world instead.
Next, you have four living generations at a time instead of three in humans. This is huge. For once, more family hierarchy. It does not matter what the pops said, as grand-pops can override him, and so on.
Even worse, the elves multiply faster than they die out. The are on an expansion tour. They need more and more resources. They fight colonial wars for the elvish oil and elvish rare metals, that are required to fabricate evlish Li-ion batteries in elvish smartphones.
If elves are not united (which they probably are not), there is a lot of friend-foe mentality. If they are already (after a huge bloodshed, probably), they need some kind of a frontier where to push a horde of youngsters that have no purpose and place in life. A frontier like space. So, expect your space-faring elves to fight wars with humans or space-orcs.
Next, high population density and big re-population potential leads to a diminishing perception of elf life. (And, by extension, of life of any sentient being, including humans.) So, the elves can kill for nothing. They are used to fight in never-ending wars and to die. Probably, the duel culture is thriving. For a reference mind-set, take Japanese samurai from the Fighting Provinces era.
Ooops, that's much more D&D drows than Tolkien high elves.
An alternative, when keeping the life span and even above life span proportions, is to change the biology more. For example, an elf can get pregnant only from her eternal love, and it takes, like, 90 years to find. Then we have elvish children at around 90 and grandchildren at around 180, which is a) well in the retirement age, and b) a bit over-extended human situation, hence only three generations at once. Problem solved!
The consequence is having a huge "bachelor gap" in the society. Elves now mature at 25 and are left for their devices until around 90 before founding a family. Interim families, long world-travel (even before retirement, wow!), yuppie career spree, going on an adventure (who said "asari from Mass Effect?"), or other things might ensue.