The key is to make sure you do it in as healthy a way as possible. Especially if you want to travel and do lots of walking and sightseeing, you'll need to ensure that you are both fit and fat.
For someone who REALLY loves gaining, the downsides to gaining can be enjoyable. Not being able to fit in a seat can be quite a turn on. However, if anyone is at the point that they don't feel comfortable at, perhaps it is time to stop, at least temporarily. At that point, you'll either miss the gaining and start again, or not go back to it.