I've had 102 usernotes in a little over 5 years, but usernotes didn't exist beyond 2.5 years ago, so I've had 102/2.5=40.8 usernotes per year, meaning I can expect to have somewhere in the vicinity of 102+40.8=142.8 usernotes in one year's time, provided I continue to post at a similar rate to what I manage now.

Joy.