Resonable explaination

NO.

I think not. If you have not been able to resolve issues certain issues over the past 5 years, there is no reason to believe that any significant change is going to occur soon. Better to cut your losses and try and find hapiness with someone else.

You didn't say if you were married, living together, or just going out. If you are married, then do whatever you can to fix your marriage, and if you can't, get out. With the other 2 situations, just get out. There's no point in remaining in a miserable relationship if you don't have to. It will only get worse if you continue.

No, it doesn't matter how long you have gone out. If you are unhappy with the relationship, there is no reason to be with him/her.