I noticed a weird thing with maintenance, padding a fleet with lower tiered ships reduces costs. Even if the total number of ships is higher.
So, with match making times being what they are, I decided to explore it.
The spreadsheet is a work in progress, and if anyone with a full fleet of Tier 4+ ships wants to contribute data, that'd be awesome (because I only have 3 Tier 4s right now and my ability to finish data collection is limited).
-> Tests I cannot complete at this time:
Tests requiring 5 T4 ships
Tests requiring any T5 ships
EDIT: And, as pointed out below, this table will likely not be 100% accurate. I can pretty much only report what I experience myself, and anecdotally there's more variation to this then I can fully capture here. Hopefully the table will be usable as a rough guide to improving your maintenance experience
Also, many thanks to everyone who inadvertently helps with this project by wrecking my various teams and I.