if you have to cheat...

4 week camino

I would suggest not deciding before hand on where to get transport.
I loved the meseta. (It is roughly the area between Burgos & Leon). It was in those wide open plains that I stopped thinking and just became a part of the landscape.
Depending how good a walker you are you can easily walk from Roncesvalles to Santiago in 28 days. I walked it in 27 days and although some days were a bit of a slog it wasn't unpleasant.
The Lonely Planet Guide has a chapter on walking the camino. The earlier editions recommended a 28 day walking schedule from Roncesvalles. I think it has now been extended to 30.
John Brierley's Guide suggests 33 days from St Jean Pied de Port.
"A Practical Guide for Pilgrims" by Milláno Bravo Lozano suggests 30 days.
Just walk and enjoy but when you find that you are not enjoying or the weather if foul or you have a painful blster and need to do a short day, or there is a long hard slog into a city (like Burgos) get a bus on those stretches.
Buen Camino.

You can save yourself a day walking alongside a busy road if you took the bus / taxi between Leon and Hospital de Orbigo.

Or save two days by getting the bus straight from Leon to Astorga. You could also skip the walk from Ages (or thereabouts) into Burgos.

I also loved the meseta, it reminded me of parts of Australia, just needed a few eucalypts and some kangaroos bounding about!

Also I don't consider it cheating to take a bus once in a while. It's a personal choice. This year I'm walking from Lourdes to Pamplona, then Leon to Santiago. My flights are booked, as are hotels in France as I'm having a 'holiday' before I start walking. However, I've just realised that I've only 18 days to walk between Leon and Santiago and, since I'm a slow walker, that's really pushing it. So, I've no doubt that I'll be hopping on a bus somewhere along the way - and with no regrets about doing so.

Trudy