I've actually thought about steeping a batch in my oven. 170 degrees is as low as it will go. Not much different than a crock-pot @ 150
You know I'm thinking this is probably fine. I just did some temperature tests and my ldpe bottles were standing up to 230-240F. They got very soft and would certainly deform if manipulated. It wasn't for long because I don't have a way to regulate temperature that precisely but a few min is pretty convincing. I was also curious about potential expansion of the liquid so i filled it up with water and stood on the side with my heel, no popping no leaking. This all leads me to believe you could throw more heat at them than would be necessary to complete the task without worrying too much.
What temperature is it at?