How to prevent/remove stains from composite resin veneers? Does staining occur immediately? (Photo)

Hello all. I have composite resin veneers on my front top four teeth. I have had to get these redone every two years due to discoloration. There are no stains are such but overall dulling and brown/yellow. I try to avoid tea/coffee and bright coloured foods but am finding that I'm constantly having to think about what I can and can't eat and feel guilty after tea, coffee or pasta. My dentist says to go porcelain but I'm worried about my natural tooth being destroyed in the process.