Grill vs. slow cooking
Simple thinks may work fast but for best result usually are needed much more complicated ways.
You can put pice of meat on grill and be done with it in a minute. Some may like that, but it is nearly charcoiled on outer and nearly raw in middle and all spice is just on top of it. If you put the same meat to marinade, then cook it in big ceramic pot on low heat for hours, then the meat is cooked equally inside and outside, the taste of spices had reached its insides too and the meat is totally different after the whole process.
Now think about Potion of Love - if you are desperate with no time and skill, sometimes even technical ethanol+some watter may bring some temporary results (or not), but good old wine and candles are usually better and combination of strong alcoholic drinks, juices, fruits in combination with sunset, nice weather, soft music and sea may work even better and last for full night, but it is still nothing in comparation with true Potion of Love, that work for whole life. But sometimes just the technical ethanol+some watter is good enought.
But cooking Potion of Love by putting some kind of igredient to a cup and microwave it for few minutes, until it boils may bring something - probably something with terible chemical result and way more side effects, than the desired result. Why it is so is simple - there is no magic, no work, no fire element, no internal resonation - just some fool chemistry.
For true magical Potion you need those ingredient carefully selected, deep magical background and both knowledge and practice of the witch and it had to be boiled in cauldron on a real and life fire (which adds its natural magic too) for sufficiently long time, so all the mixing and timed adding of ingrediets can create something magical. (Automatization would not work for obvious magical reasons)
Now if you have old cauldron, which was used this way many times over the years, all the magic around it would soaked in and slowly transform it to actually magical item. Using the same approach would fix in and helps to harmonise the process of magical transfer according it user personality - so it is also the reason, why cauldons are usually inherited by child of the original owner (or somebody else, who helped for years with working the cauldron, is accustomed to the style and the cauldron is already harmonised whit her/him).
Fire magic if fierce and fast and the cauldron is one of way to tame it and use it more consistent and harmonised way inside the potions. Old cauldrons are especially good at it, as they are trained by generations of witches to do so. So they feel a lot heavier then their weight really is and they resist to fierce fire and accumulate its power to slowly transfer it inside in harmonised way, where the "tamed" fire power oscilates in the whole potions consistently, taking the best out of ingredients and trasforming it really strong and elaborated potion. But it taks a lot of time to hamonise all those flowers, eyes, liquides, fire, will and magic. So the potion is in the end really well prepared, but it takes way longer until it even start boiling, not mentioned until the fire magic is fully and flawlessly merged inside.
On the other hand new caulron is not much more, that metalic pot, which simply distributes the fire power somehow around its content, not caring how. It is also the reason, why new cauldrons are more prone to singe some ingredients, if not constantly stirred. Old pots prevents that usually.
That results to new pots to transfer the heat and the magic of fire inside a way faster, but also a way less coordinated and effective way. With good skill, lot of stirring and some practice you can make a potion in it faster, but it would not be so harmonical, potent and elaborated, as is possible to get from old, trainded cauldron.
Many times it is still "good enought", sometimes the time is even so crucial factor, that you accept all other problems and sideeffects, like when you are making a lot of healing potions for already wounded fighters in war.
If you are making Potion of Love just for trade, it is ok, if it would "works for any two, who will drink it together from one cup" and over years affected man would lose some more hairs and woman get some more weight, so new cauldron fits well.
But if you want to make Potion of Love to bind specifically princess Eleanora to prince Fernando and nobody else, then there is no place for "any two" or some sideffects, so the choise is straighforward ...