As long as your pocket (and your physicial fatigue) can support this behavior and that you are going to utilize the membership benefits as much as you can in the current and the following year, I see this (mattress run) as a pretty smart move (being a top tier elite means a lot at a brand hotel - it can make a world of difference in terms of experience).

On the other hand, there is no point of reaching an elite status (let it be hotel status or airline frequent flier program) if one is not going to utilize the benefits in the following year of the qualification. Why fly and spend so much if your travel isn't going to happen much in the following year (there could be one exception - if one is very close to acheiving the next tier status, then one or two MRs can be justified)?

But in the end, all comes down to personal economics. YOU can only be the judge of the cost effectiveness of your spending on MRs.