Absolutely - my own skills are now probably 2x or 3x what they were....Im quite astounded. Yes it helps with currency...but there is another advantage of instructing over any other form of flying....that day when one of your students says 'yeah I had a really problem with that...but youve sorted it out now.' - I dont want thanks, I just want to see my students progress and be successful - but nothing can top that 'warm glow' feeling you get when you receive true gratitude from a student that you have *truely* helped.....
I also get to fly with a lot of existing PPLs at one of my clubs...and this can be *really* good fun...my aim as an instructor on these check flights is threefold...I try to make sure they are still safe (to a good standard) - for their own & their passengers sake as much as the clubs; to help with any questions/issues they may have; and finally to try and give them at least one tip/new experience that they can learn from and take away with them. Some of the most rewarding flights have been with these existing PPLs where I have succeeded in giving them something new...
There is *much* more to instructing than merely hours & aircraft...