Iwould suggest you keep expanding up to the 250 max then with any sim cash you aquire use it to expand capacity in your shops. This way you can use the shops as storage for items also
You don't get SimCash for max storage expansion. At least, I didn't.
Max territory expansion gets you 35 in SimCash (Growing City achievement), but I don't see an achievement for storage.
Max storage is its own reward.
Besides being able to manage inventory effectively, I also enjoy selling expansion items my Sims continue to give me. They get snatched up before I have time to exit the Trade Depot. Like tossing raw meat to a pack of jackals.
