It would be ideal if players submitted ongoing
"I'm learning this..." in their downtime activities each month, or at the very least,
"I'm starting this..." and
"I'm finishing this..." at the beginning and end (actual purchasing portion) of the process. A brief few sentences regarding whom you are learning from and the justification, would also be a pretty basic requirement.
As with any XP spend, if the staff has any questions or feels something in the spend is incomplete or needs to be addressed, one or more items may be challenged and/or denied. For example: A character may need to spend more than the normally required time (at ST discretion), if her schedule has also been jam-packed with learning other things during the same timeframe.  In a case such as this, an additional
"You've been way too busy lately and it's going to take you another month or two" delay may be imposed.
It comes down to good roleplaying, and that is how it will be policed. Is there anything wrong with allowing the prescribed amount of time to pass, then submitting an expenditure to up a level of Ability (for which you at least have a teacher, at minimum)? Well, not really, if you want to be lame about it. Good roleplaying involves real discussion and learning among characters. Who are you learning from? When are you learning from them? Daily? Weekly? Multiple times per week? How does the time spent doing this, factor into the other things you may be doing this downtime? Particularly if you travel to other games a lot... These are all things to consider. Be creative! It should look like you tried!
Bottom line is that if the process you show is bland and mechanical, lacking at least minimal interactions/scenes, then you risk losing your good roleplaying XP that month... And that adds up!Â