What is the maximum value of a number whose digits add up to 10, if you are allowed to decide the base of the number.

I have to put in place a couple of rules:

You can’t use any zeroes. Clearly you could make a number arbitrarily large by adding a string of zeroes at the end.

The first digit must be just one less than the base you are using, otherwise you could just have, say, the number 55 but say it was in an arbitrarily large base.

The decimal number 91 and the binary number 1111111111 both follow these rules, however they are not the maximum. What is?