Two questions concerning maintenance fees

[kcclieou]

While I understand that the exact formula for maintenance fee calculations will never be released, I have the following two queries concerning the issue, out of curiosity:

1. Would the maintenance costs of two different variants, with different unit costs (because of a slight difference in their performance), of the same model (e.g., an Airbus A319 with 2086nm range versus another with a range of 4254nm, both with IAE engines; or two Boeing 767-200ERs, one with a range of 5310nm and another with a range of 7658nm), differ? I read that the maintenance costs of two different variants of the same model and with the same performance would be the same, but no one ever spoke a word on this.

2. I recall that the maintenance fees would amount to a fixed percentage of the new aircraft value at a given aircraft age, and that this percentage would increase as the aircraft ages. Is this 'fixed percentage' the same for all aircraft, or does it differ for different aircraft? For example, would the maintenance expenses of an Airbus A330-200 be very much the same as that of a Boeing 767-200ER of nearly the same unit cost and of the same age, or would they differ by a substantive amount? Or would that 'fixed percentage' be much higher for a Boeing 767-200ER than a Boeing 737-700?

Thank you for enlightening me on these issues.

[dktc]

1. Different engine variants are treated as different planes, so the maint would be different.