I love this—"I have a great tent… it just leaks." Hmmm. I think the leaking part is what the tent is supposed to prevent!
My own view is that the tent is kaput. Tents don’t last forever—the sun breaks down the fabric, inside storage can lead to mildew that eats the material, and so on and so on. Re-sealing the seams is one thing. But the leaking fabric tells me that the waterproof coating has de-laminated or worn away, which is fixable in small patches with McNett’s Gear Aid Sealant ($10). But you’d have to paint most of the tent. Besides, even though the fabric may LOOK fine, chances are it has lost much of its tensile strength. The whole thing could just rip to shreds in a strong windstorm.
There are a lot of tents out there that offer good quality and won’t break the bank. A good example is the Eureka Tetragon 1210 ($239). It’s a two-room (or one—it’s up to you) that sleeps six. Polyester floor and fly, fiberglass frame, good ventilation. Eureka’s Suite V6 ($299) is also a two-room, six-person tent, and adds a covered (not fully enclosed) screened front porch. Or, there’s Eureka’s big Copper Canyon 1610 ($380), which sleeps six, and has two rooms, AND screened front porch.
There are others. Coleman’s WeatherMaster 4 ($229) sleeps four, and has a screened side-room for buggy conditions. Or there is the GigaTent Mt. Kinsman 8 ($250). A real bargain—a big eight-person tent with three rooms and a screened porch. That’s pretty luxurious!