Eh, reading a chapter never takes more than 10 minutes, and it's once a week. Just as long as you know what sites to use and release dates, you'll be fine. Hell, you could even get an official subscription to One Piece by then, as being an adult you should have an income.
I'd like to believe that if the theory that the final saga/arcs of OP will be that massive war, that the second timeskip would be a period of several years where everyone makes their final preparations. Then an adult Luffy and co. wage war against the WG. Basically, it's years where the WG thinks they've beaten the pirates and are preparing to have their perfect world. Then boom, Luffy and co. show up to kick ass.