These go on my Lowden F50 guitar and they suit the instrument well. Changing strings less often while maintaining good tone is an absolute luxury.
It wouldn't make sense to buy these if you're prone to breaking strings, aside from the expense, it would defeat the purpose of using something built to last. Also, if you're on an instrument that doesn't sound good to begin with, there's not much to be gained putting these on.
If you split your time on more than one guitar these are great. Instead of opening a case after a couple of weeks to find discolored and dead sounding strings that won't tune true, you pick up right where you left off.
Put these on a nice instrument and they will sound great for a long time.
