How to avoid getting a numb bum

We have a couple of options available, they range from cheap to massively expensive.

Folding a towel and placing it on your seat usually gets you to go a little further than normal, I tried this and basically gave in and bought a Corbin Seat.
Airhawk is an inflatable seat very good, and if you own more than one bike you can use it on all of them, no reason why the Airhawk shouldn't enable you to do a 1000 miles per day.
Sargent Seats are very good quality as are the Corbin Seats, these I feel are doen to personal preference. I have personally invested in the Corbin seats and they made my journey from John o' Groats to Hertfordshire easy and I managed to make the entire journey in 14 hours.

When traveling at low speeds and you feel confident enough you can stand on the pegs to give your bum a bit of a rest, but the above mentioned solutions are safer albeit more expensive.

Good luck hope this helps.