I don't know how often mid-patrol resupply would have been, but suspect it was rare.
As far as the sub tenders, they never came out to you, you always go them. They were a rapid and convenient way to set up forward bases as territory was taken from the Japanese (and they could get out of the way if trouble returned to the area - beats loosing the investment in a land-based base). Typically, as islands were taken and occupied, a sub-tender would anchor nearby to provide a base closer to the action, thus saving you from an even longer trip back to a major fleet base.
They did not deliver, however, you have to pick up your order
