I want to agree but the problem with that on this is that it can be gamed by buying one month, using that until a feature entices you, and then buying another month.
At least you'll have paid for 6 months right away; and if you lapse, when you go to renew you pay for another 6 months upfront.
If you're going to all this trouble just to skimp £100 per year on your main development tool you're probably the type of customer who will simply not buy into a SaaS model anyway, so there is no point in chasing your pennies.
You could unofficially make the "skimping" into the reduced price option, removing the current "personal" licenses and removing complexity. Cheap "Personals" will pay a 6-months fee once a year or less, losing updates, and "Companies" will happily pay full whack (because they value predictability and opex vs capex) for the full monty. Win-win, and nobody gets hurt in the feelings.
