There's no reason to subscribe for six months at a time unless you want to have a large number of characters. The reduced price per month is just the same price you pay month-to-month on an entry level sub, which gives you the full experience with a limit of 8 characters instead of 40. Alts don't share quest progress, so if you find a single pass through the MSQ daunting then you're unlikely to be creating that many extras.
If you're enjoying the story and want to continue, do it. There's good stuff ahead, and your friends can join you at your own level to complete dungeons or side content. They may even have their own need to play the content you're on, like collecting glamour or filling out the weekly "duty bingo" card.
If you just want to be at endgame and explore, then buying a skip will let you do that, while abandoning the game completely will not.
It's entirely up to you, but I wouldn't base my opinions on what some internet people think over my own taste and that of friends who like similar games to me. Don't fret about the exact number of quests, just play it and keep going for as long as you enjoy playing it. (Stormblood is a bit of a low point though.)