I'd be much more concerned about your front wheel and front fork, then I would the frame.

If your front wheel or fork breaks while riding you will go down faster than you can think. All your remember is a tiny sensation that something was going wrong then you'll be on the ground.

If your rear wheel goes out it happens slower you usually have a chance to get a foot down.

If your frame breaks it's a triangle, so you're still kinda supported by the rest of the frame. I've had a bottom bracket rust out while I was riding and other than making scary noises it was fine, I was able to coast to a stop, then coast on the frame part of the way back home.

I'd replace the front wheel and maybeish the front fork before I'd worry about the frame.