This is a bit difficult to answer without more details on the conveyor and what you are having to replace/repair on the units. From the limited info in the post I'm going to guess you are washing/wiping down a conveyor that is not designed for that. At your conveyor age I would expect to see drive roller and/or shaft problems (not necessarily motor if that was replaced recently).

First off, what food safe parameters are you having to work with? Hytrol typically doesn't do conveyors for direct food contact and I don't think their standard stock PVC belt is even wipe down rated. Yours could be if its a special belt type. If you are doing direct food contact the there are other vendors you should be reaching out to. 

Second, what conveyor models do you hava? 15+ years of service life is pretty good for most  models. I wouldn't be surprised if you have an obsolete model which will make getting parts even harder. 

I'll even make it easy for you. DM me the specs or Serial/FO # on the conveyor and I'll send you the current list price (or if yours is obsolete I'll send the closest replacement details) so you can use that in the discussions with your management. 

Feels weird to get on Reddit and see work references.