It is absolutely a great thing to do.
Everything you do will be faster.
The longevity of the drive is not a factor. The longevity is determined by how many writes you do to the drive. They are designed for at least 5 year's worth of writes to a heavily updated system, far more than what a normal user would ever do. Even if a drive reached it's write limit, the contents of the drive would still be readable, allowing for the time to clone the drive to a replacement. In 5 year's time, current drives will be obsolete.
If you need 150gb of space, a 256gb drive will serve you well. It will perform better and last longer.
I had a Intel X25-M 160gb drive as my only drive. I gave that system to my son, and I miss the speed terribly. I am using a temporary velociraptor, and will get a crucial C400 or vertex 3 when they become available. Hopefully in a week or two.