lovelysharon: Yes, I realised when Hrqls posted that you were continuing the topic.

30 days in January or 3 days per month would surely be a choice for each user to decide. But even if 3 days per month were forced upon people there shouldn't be the problem that you fear, except right at the start of membership. If you take a long holiday in February but none in September through January then you'd easily have built up enough to take 10 days off. It's only in the first year that there would be any problem. If I were implementing that system then I'd avoid even that hardship by starting people off with 10 or 15 days and then adding the 3 days per month thereafter. But giving the choice is better.