However, you ask "can they be kept". Yes, they can. Should you keep them indefinitely? osucpa provides good advise. I recommend not keeping documents beyond the retention period too.
However, make sure you look beyond Reg B. There are many other regulations that may apply that require retention beyond 12/25 months. For instance, BSA & RESPA are 5 years. HMDA is 3 years following submission. You have to look at all of the regs the type of application is subject to.