When do you thinks the best age to make aliyah?

it really depends. if your single and your hebrew is good, i would say right before college so that you can make friends and get into the society easier than to come after that.

if you are married, then come before your kids get too old and then you say "oh, they are in the middle of school, we cant come now" and then that becomes your mantra till you die....

what is your situation? married? single? finished school? still in high school????

I agree.

Usually the worst age to make Aliyah is high school age.

It's definitely logistically easier to make Aliyah while you are single. Though it maybe emotionally easier when you are married (can't say for sure.) If you have family here it definitely helps.

Another point to consider. You'll want to be financially stable when you go - which means you have savings and the potential to earn a living after those savings run out.

OTOH, when you're young, it's easier to manage on little money. So it's better to come with less savings when you're 22 than to waste your 20s in chutz trying to save up. The longer you have to build your career in Israel, the better.

Whether to come before or after college depends on your level of Hebrew and what you want to study. If you're going to be a lawyer, for example, you might as well learn the Israeli system straight off. But if you're studying something unusual or very prestigious (it never hurt to get your engineering degree from MIT) then that might be best. (Remember though, if you're male, coming very early might mean the IDF; if you have a good profile and are eligible for 24 months or more, you might be worth the effort of training.)

But overall, younger is better.

מצוה הבאה לידך אל תחמיצנה

i think its easier the younger you are because you're single, can manage on very little, and in regards to army service or university its makes things much simpler, its easier to go in at 18 when you have no one to support, then when you are 24 with a wife and two kids. as well finding a house/apartment isnt as big of a problem. but in reality it all depends on the person

Best? As in ideal? Before you're old enough to remember it. But b'dieved either right after high school or right after you get married depending on what job you want to do, what kind of educaiton is important to you, and what type of person you want to marry.
Personally, I think if all the people who go back to חו"ל to find their bashert who will also want to live in א"י and then "somehow" just get stuck and say that they don't fit into Israeli society or have big issues with חינוך in Israel would all stay in Israel when they were single, then all together, there would be more of a "normal" community of all those people who they had to go to America to find normalcy still in Israel. Please excuse the run-on. And Israel is a lot smaller than America, Jerusalem easier to walk in an afternoon than NYC... There are less places for your bashert to hide.

From a family-with-kids perspective, we were told the absolute latest to go was before the oldest is 10. After 10 years old kids are way too entrenched in their school/community/friendships to move to another country without it being hugely difficult.

So our oldest is b'H 8 and we came this past summer and they're all doing pretty well absorption-wise. We live somewhere with a pretty small Anglo community, so they're really forced to integrate and learn the language quickly.

We parents are having a harder time, it seems. To be expected.