Hmm, surprised no one else has chimed in. But in my opinion, if you are not a heavy spender, then there is no reason not to level freeze. If you are F2P, you level freeze, if you are a medium spender, you should level freeze. The pros to level freezing severely outweigh the cons.

The major reason to level freeze is to get into a favorable SWB bracket where you can consistently get the Top 3 every time. How I currently level freeze, I do not do anything that gives a lot of EXP. No Ninja Exam Sweeping, No 9 Tails Invasion, No Wanted Missions, No Activity Claiming from Daily Practice, and No Anko Test. If I do all of the other timed events, I can get the max amount of Sun Coins offered per week and get around 60k moon coins per week. Not really missing out on that much except Strange Stones and a couple of little power items and magatamas (but mine are at level 7 or 8 anyways right now and it would take a while for them to level up), and coins for doing 8 inner gates.

Its EXTREMELY worth it for me. I can pretty consistently get 1st or 2nd in my SWB and pretty regularly get the Bully of the Battlefield Title from highest SWB points. That has allowed me to get 300 Advanced refines by the time the rebate comes around. The rest I got from maxing out the Lucky Board Optional Refine packs. I saw my pos1 int go up 2k points from that.

Its all up to you what you chose not to do and what to do.