So, a relevant thing happened in my latest playthrough:
I still have yet to kill Plantera, and I was just celebrating my Ankh Shield completion (first time I ever completed an Ankh Shield pre-Plantera!) after a bandaid dropped from an Arapaima in the jungle.
I spent that following night looking for fireflies (only got 5 to spawn the whole night, and it was a new moon too!) and what did I see come 4:30AM?
"A Solar Eclipse is happening!"
I was totally unprepared for this. Sure, I had a Godly Yelets, but that's the only real good piece of equipment I had other than my Daedalus Stormbow (which did not work anywhere near as well as I thought it would have, the mobs are too small and half of the time the arrows and stars won't hit them).
Anyways, I killed 5 Mothrons and got 1 Broken Hero Sword. The Mothrons gave me no trouble whatsoever; I was only wearing Turtle Armor and using a Yelets with Yo-Yo Bag. At no point was I ever in any real danger of actually dying. I think I got hit once with Mothron's charge attack (it did like 80 damage). Sure, that hurts... but they are also hilariously easy to avoid if you just fly circles around him, it can't hit you and it will eventually lands to lay eggs and you land next to it and kill its eggs while hitting it with the Yo-Yo.
Easy-peasy.
Sadly only one BHS dropped, but hey. If another had dropped, I would have had a ridiculously awesome weapon for Plantera! I bet I could probably fish up another one if I camped out in the entrance tunnel to the Lihzarhd Temple and killed Lihzarhds for Tablet Fragments and pop another Eclipse, I'd probably have a Pre-Plantera Terra Blade just for kicks. This could be done totally legit in any playthrough that gives you a long enough entrance hallway to the Lihzarhd Temple as merely standing behind Lihzarhd Brick Walls will spawn Lihzarhds nearby if there's enough room for them to spawn even without unlocking the Temple Door.