You tried it?

Yes.

In my experience the boiler will come on every hour or so, which is
wasteful.

It will use very little fuel to do so on a modern modulating boiler,
especially if the pipe runs to the cylinder are short. I have no qualms in
running hot water 24h, and I'm relatively interested in environmental
concerns.

In any case, if it is a problem, it is easy to stick a one channel
programmer for the hot water.

Christian.