I usually only manage to complete 2 missions after getting the Reaper IFF before the Collectors attack — but the time I tried to speed-run it and complete the minimum number of side-missions possible, it made me do more.

If you want to maximise Legion usage (without losing crew), then do the bare minimum necessary to survive the Suicide mission, and complete most of the content with Legion after destroying the Collector Base.

If you don't care about saving the crew (bar Chakwas), then rush to the Reaper IFF mission, activate Legion, and play all the missions you want to. The SR2 will be pretty empty though.

What if I don’t talk to Legion before his loyalty mission? Will that delay the countdown a bit or does it matter?

Nope. Regardless, you still only have 1 maybe 2 before you need to book it to the relay.

Ahh Legion. Wasted potential.

If you don't care about the crew, you can just wait it out. I did that the very first time I played the game. Which is a shame you can't really use him on most of the base game if you want everyone to survive and save all the crew.

I can only do 1 mission after gaining Legion before Edi and Joker mess up installing the IFF. But if you want to do missions with Legion you can save a lot of them for after you do the suicide mission. Bringing him to Tali's trial was one of the best things ever especially as it is remembered in ME3. Bringing him to project overlord is fun too. And getting him to walk around the Citadel and help with the geth infiltration security check is hilarious 😆

If worried about people dying during suicide mission just make sure the 4 key people that are needed have loyalty

Thanks guys I’ve decided to do Tali’s and Legion’s loyalty missions first then do Overlord and the two N7 side missions that involve the geth after.

Any DLC missions, outside the Loyalty missions don't impact survival of members, so you can wait and keep those up till post Suicide Mission, but the Loyalty missions usually have inter-character dialogue and interactions which are the best in the game, so kind of sucks they did this.