I have been doing IRL air inflation with a bike pump for a couple weeks after years of lurking on this site, and I have been having troubles staying inflated for more than a few minutes. I've heard of people holding it with no issues for hours at a time however.
Is this something that comes with being a noob, or am I doing something wrong?
Well, yes and no. Your not experienced and havent developed the muscles for retention, and if your using air you wont exactly get used to being inflated, as in, you will still probably get cramps and not really adjust. Higher capacity and retention comes with practice and time though.
Also, might I suggest using an aquarium pump? Everyone I've talked to that has tried it prefers it over the bike pump.
(Not on here too often, replies might be slow.)