My most recent character is my first one to use Energy Weapons as his main combat skill. I had heard that the ash or goo piles caused by a critical hit with an energy weapon will never disappear and eventually the amount of piles spread throughout the gameworld will bog it down. Is this true?

Sometimes. Bout 99% of the Ash and Goo piles will go away but sometimes they will stay

What platform are you playing on? If on PC, there are mods to get rid of the ash and goo piles. Some people on consoles have had a lot of trouble with ash and goo piles piling up but in my console experience, once I turned a respawning enemy into a pile of green goo, any time I came back through the cell in the future and killed him/her again, the actor's inventory would transfer into the old goo pile and a new one would never be created.

I never had any of the ash/goo piles disappear on me. Once made, they were there to stay.

And for your info hackworthy Try NOT to shoot anything in a doorway the goo pile can prevent you from leaving that room. So be careful

Unfortunately it has been confirmed, The Super-Duper Mart is still full of ash piles from my pistol crits. And it has been 2 weeks in-game since I was in there.