yup. 35 ft. spring lines are a nice thing. there WILL be a time when the extra 5 feet will be what you need to tie up your boat properly. And if you are missing that 5 ft. you will curse yourself for not paying the extra $10 (or however much it is) for a line that is the right length.
Also, there are times it is nice to be able to double the line back to your boat so you can cast off from your own deck and pull the line back on board without needing to get on the dock.
Also, there are times it is nice to be able to double the line back to your boat so you can cast off from your own deck and pull the line back on board without needing to get on the dock.