Altberg say the worst thing you can do is leave your boots dirty with mud etc so washing your boots with water after every day's walk would be a good start.
You could look out for a small tin, like say a small vaseline tin, and fill that with with whatever you use for your boots and rub it on with your fingers every few days.
Obviously give them a good load of bootcare before you start

I have just got some new boots and I have been told they will last 10 years with re-soles if you care for them right, but I guess my laziness will condemn me to buying another pair in four years or less!

I'll be doing a continuous walk for a couple of months in the summer (https://sponsoramile.ilovefreegle.org). Obviously I will be trying to keep my pack as light as possible, and on previous long walks I've not really taken anything with me to take care of my boots, e.g. any boot cream for reproofing.

I was wondering what other people do? Nothing? Smear them with butter from a bed and breakfast?