If you need to replace the hose, stay away from the plastic stuff. Flexible metal is a code requirement for a good reason, it does a good job of temporarily containing a fire, if the lint ignites. I didn't give it much thought until I had a bathroom exhaust fan catch fire. The flames extended into the metal flex duct and the fire quickly extinguished itself. Had it been the typical plastic stuff, that was used in most older homes in my area, it would of quickly melted through, and had plenty of bone dry attic framing to ignite.
Also, the comment about breakers not doing well after repeated tripping is correct. It sounds like it's tripping on overload, not fault, so it's not as hard on the breaker, but it still isn't something that you want to continue doing. As a general safety rule, do not face the breaker, and look at it, as you are resetting, particularly if it's a breaker with a history of frequent tripping. Keep as far back as possible, turn your head to the side, and look away as you reset. Breakers will occasionally fail by blowing apart during resetting. It is rare, but it happens. I only experienced one, in a long career as an electrician, but the are memorable, to say the least. Finally, it appears that the diagnosis of poor air flow and heat build up is probably correct, and needs to be addressed first. However, don't discount the fact that the breaker may be failing. Sometimes swapping out a $10 breaker is all it takes to solve the problem.
