It is not unacceptable to ask for updated payment details every so often, so users don't generally have issues with this and it saves you from having to store t

It is not unacceptable to ask for updated payment details every so often, so users don't generally have issues with this and it saves you from having to store the actual card details. You just have to store the token as others pointed out. Also, if you do integrate multiple providers early on, you can break users up over them so that again your risk is minimized. This does come with some accounting pain, but it mitigates some risk so it is worth it. So essentially if you had to move away from one vendor it isn't your entire customer base all at once.