....never tried it myself but there are quite a few great products out there that will last 6+ months and even some that have proven to last for a year or more. The fact is that no two scenarios are alike. ....environment, where the car is stored, weather, where the car is driven, products you use to maintain the car, wash techniques, etc. all play a role in how long an LSP (last step product; wax/sealant) will last.
Personally, my take on the whole thing is that even if it turns out that it doesn't last that long, at least you're using something to help maintain the finish. If it's cheap enough, why not buy a bottle and give it a go? Maybe apply it to one panel and your favorite LSP to the rest of the car to see how it compares?