Anyway, as for seam sealing, it's necessary as often as it's necessary, which should not be often. The Swallow ($359), a heavy-duty three-season tent, already has taped seams. So as long as they're holding up, it's fine. I've never actually seen tent tape delaminate, although of course it can. Should that occur, my first step would be to ship it back to Marmot and have them re-tape the seams, as I think using an after-market sealant would be a waste of time. Of course, you also can re-coat the floor, which may prove useful. Kenyon makes a product called Recoat 3 which is designed just for that purpose$8 for a ten-ounce jar, which should be enough for the Swallow's floor.
How to ensure your tent lives as long as possible? Three steps. One, keep it out of the sunpitch it in the shade of a tree if you can. Two, keep it clean. Sponge-mop it after any use where it gets dirty. Three, keep it dry. Store it loosely in a breathable cotton bag. And NEVER put it in a clothes dryer.