I never noticed this until today, but it turns out htop has a little easter egg:
When your server hits over 100 days of uptime, htop congratulates you with a little exclamation point :)
sprintf(daysbuf, "%d days(!), ", days);
Worried me initially, I thought something was wrong! :) Or perhaps you could say it is - servers ought to be getting rebooted into new kernels more often!