Tonight I tried out the BASE MENT seed. It's a pretty fun, if completely useless time waster of a seed. You can't win. And you pretty much always end up getting bored after an hour or two once you become almost completely impervious to all forms of damage, so it's best to choose a ending point...
In my run I chose level 50. By this point, actually by about 30 levels or so earlier, I was completely indestructible unless I tried to kill myself. And even then it was impossible in my case. I had items that did everything. My little army of blue spiders was unflinching and took out entire rooms of enemies in seconds before I could even shed a single tear. Earlier I even had a cat head that gave me flies. The flies always made it to the enemies first and I found myself constantly refilling them when the spiders were a much better supply, so I let it go eventually. My little deformed scapegoat came too late. By the time I got him, (Apparently from a Pretty Fly pill) I was so overpowered the enemies themselves didn't even get time to fire either, so he only came along for the ride, and I was glad to have him. On the very last level I picked up Tiny Planet and finished the job. This was the end. I now had giant multicolored shielded randomized tears circling my head forming a complete shield around me and my many followers. There was no reason to go on anymore. It was over. Oh, and by the way, I even had an item that made me actually invincible at random 90% of the time I entered a room, and another item that let me smash through rocks and poop with ease. In the final 10 levels I just gave up exploring and tried to get to the boss as fast as possible. At which point my friends would make quick work of them, and if not, then my invinicibility would. Even Bob's Brain couldn't stop this train. (I was hoping it would fuck me up so I could end my run. But it didn't do a damn thing except tag along with me.) And for some reason I only ever got a single cube of meat. But at one point I did have 12 whole hearts. (And plenty to sacrifice for better items.)
Seriously, the Scape Goat/Punching Bag familiar is my favorite thing ever. He's so adorable.