Some people might find the answer to be obvious (yes) but I’ve rarely found it so. In fact, this is a question I often find in the linux community (regarding linux going mainstream, not lemmy) and people are pretty split upon it.
On one hand, you may get benefits like more activity, more content, more people to interact with, a greater chance you’ll find someone to talk to on some specific subject.
On the other, you could run into an eternal September like reddit, where Lemmy would lose its culture, and have far more spam and moderation issues.
I don’t know, what do you think?
Lemmy.ml as an instance, yes, but not too much.
Lemmy as a federation, yes yes yes, as much as possible. I don’t think there is something I would consider “too big”. But maybe I would prefer it not to grow too fast in order for it to have time to react and adapt to a diversification of culture and even usages.