I generally don't use afrin or sudafed more than 3 days at a time. Both medication can cause significant raise in blood pressure so if you already have hypertension, be careful. With afrin, I think you can also get a rebound phenomena when you stop the medication. I think either medications are ok for a weekend trip but I definitely would not use combination of the two. For a longer trip, if I need to use something, the long acting non drowsy antihistamine such as claritin, zyrtec, allegra type medicaiton would be safer (well, as long as you don't fall asleep underwater). Sudafed and I believe, afrin as well, may also cause reverse block when you ascend if the medication starts to wear off underwater.