Mine has a bit of a 'kick' somewere high up the range (don't know where as my rev counter doesn't work, but I would guess it would be about 5000rpm as max power output is at 5300rpm). After this, it tends to get a bit flat, and you can feel you need to change up. You'll know when it happens

Happens at approx 40-50mph in second and 60-70mph in 3rd.
'Will it damage an old engine' will depend on what condition it's in, how well it's been maintained and how well it runs, amongst other things.