Why Won't my 6 Front Top Veneers Stay On?

I agree with Dr Neuhaus,  for your description I believe it is an occlusion problem, which causes the veneers to come off that often, it means that the own force in your bite is causing it, probably combined that maybe they are not shaped in a way that the veneer can hold your bite pressure. I also agree that maybe you can have better results with crowns. 

I have a question, are you using a nightguard? are you a grinder? this is important info to find out what is causing them to fall off. Maybe you pressure too much your teeth at night and this is causing the pressure to literally pop them off.

This is very unfortunate - veneers usually have a makeover type of feeling for the patient and it doesn't sound like you're getting a realistic experience with your veneers.  The problem is either the way the veneers are being bonded, the remaining tooth under the veneers, or the way your teeth fit together. It sounds like you have seen your dentist several times.  I have to suggest a second opinion, even if you stay with your dentist, just find out what is going on.  See someone with experience in cosmetic treatment.

I agree these sgould not come off like they have. Are these no prep veneers(i.e. Lumineers) or regular porcelain veneers? I would have you go for a second opinion to ensure the teeth were prepared correctly and the bite is correct to give them room. Good luck with treatment.