Keeping all your immigration documents is an extremely important thing to do. More important, is to keep your old international passport no matter how old. An old passport shows your immigration history and past intentions. If you have an old passport even if it has no visa on it will demonstrate to the visa officer reviewing your case that you have had the intention to travel in the past and that you were not just looking to travel when your recent application was made.
Thus it is advisable to include copies of your old passport data page and of course visa/stamp pages in every application. This will improve your chances tremendously.
We included all client’s passports dating back to 1990, which made the application successful.