Yeah, I don't use it at all for the reasons you've explained, but then again I'm not making curries everyday. Yeah, just the one cover. I love curries and make them all the time but all my spices, which are many are in containers in a cupboard.
Both times I've travelled to India I've stayed in what was called a "homestay" where you live with a family for the most part where I also had the opportunity both times to cook in their kitchen after they found out I was a chef and the marsala dabba was a prominent fixture and used all the time at every meal. It was basically why I bought one but when I got home I didn't even bother to fill it because I knew I wasn't going to use up the spices fast enough, especially when I like to grind my spices anyway.
Also the spice blends the families formulate are unique to their area, family recipes, preferences that kind of thing which will be different all over India so a family in Rajasthan would select different spices than families in say Karala and I'm more inclined to change the mixtures depending on the type of curry I'm thinking of making so it would be more than likely I'd be reaching for spices that wouldn't be in my particular dabba, but that is just a thought I had later and another reason not to use it.