I was being tongue in cheek, but seriously, you don't really need a third one unless you want to get more Xs and TIEs at a better price. I bought it because a local comic shop had them on sale.
At first, I was going to stop with 1 core set and 1 of each expansion. Then it was an extra core set. Then an extra Y and TIE advanced. Then a third core set. Then another Y and TIE advanced.
I will probably buy my final TIE today.
It's crazy. I think that the delay of wave two helps me to want to fill out most of the options possible in Wave 1, for sure.
However, my original thought was more practical, around the lines of "How many ships might I really put on the table at once?" And knowing that the Wave 1 ships will be displaced by Wave 2, in 100 point builds, I already have way more than I need. But I also discovered that massive games over 100 points are pretty cool too, and you need a lot of Imperial ships to make that possible.
Be seeing you.