This is exactly what I'm having a hard time getting past. I know I could easily fill that 2nd locker, but is it really worth $200/yr plus the cost of multiple visits? I don't know.
So for those that have 2 or more lockers I ask you this. Is it all about the convenience no matter the cost or is it to save money on luggage fees?
Convenience. Definitely.
It's nothing I could ever justify with a spreadsheet. It's just nice to know that the things we'll need will be down there, and I don't have to deal with the 5-page killer packing list each trip.
I will relay, though, that an up-to-date inventory list is vital. Ask me about our trip this past July for which, unbeknownst to me, my partner packed no socks, shorts, or shirts for himself. Guess what was no longer in the Owner's Locker? We couldn't close the lid the year before, and had brought those things home with us. (One of the reasons we were having a second locker delivered.) We didn't have a car, so the next three days became a constant argument over, "I'm not going to pay that for a pair of shorts!" and "No, the shirt has to be nylon because cotton makes me break out," and "No, I'm not paying for a taxi to
Walmart." I kept begging him to let me just run out and buy some new clothes for him, but he was having none of it. (I would have gladly paid the price of the taxi and new clothes to make the whole situation just go away.)
Fortunately, friends were joining us for the second part of our trip and had keys to our house. They brought his stuff down with them, and I could stop washing his one outfit every night.