I showed 1 year monthly statements on Checking account and 2 year end statements on same account. They asked for tax return. I provided my last one which was 4 years before. I also provided an executive summary describing my situation.
I use traveling mailbox. They scan, store and forward. Most items I just print out from the scan pdf. Others I store.
If I go to the US, I forward to myself there. When I have enough items, like once a year, I will forward to Thailand. The max. I ever paid was under $10 for the forwarding.