I think your formula is ideal for the older, more experienced walker. Part of the trick is that your guys take the pace from the participants, rather than Alpine guides who lead from the front!
Keep it up!
I have probably had enough of end-to-end trekking at the age of 71. Your formula allows for the odd day off as well as a mix of easy/medium/hard grades. I will book again next year, having done Tuscany already this Spring.