We do a bit. Our latest version is - choose the rooms you want to cover (thinking of going to whole house only), you pay half the normal clean & protect price on the day (we now only do it with protection), then you pay 1/12 of the normal C&P price every month (so 6 months after the clean its equals).
We used say we'd do one highlight clean after 6 months, then a full C&P at the anniversary, and so on. Now we still write at 6 months with a reminder, but they are welcome to call us out to do anything they want doing in the covered rooms at any time. So she might want another full clean done in 6 months, 'cos the in-laws are coming, or whatever. She will call us if she spills a drink, or maybe 1 room needs doing 3 or 4 times a year, but the others just once.
If they like it, they love it. We haven't had a serious push at them since we've evolved the latest version - we found expecting to come back every 6 months was just too much for the customers - they don't want you that often, but it does mean that even in the worst month you've got cash flowing positively, the competition don't get a look in, and you get the value of a full C&P every year.