I'm in the process of making my own because I hate how they aren't flexible.
What is you salary increase?
Um last year it was 2%, this year 15%, guessing 10% next but I 'know' it will drop to 35 for a set number of year before I hit the next bench mark.
Whats your 401k contributions yearly?
Well, right now it is 24%, will go up for 2 years, drop when I have kids a little, go up in 4 years when Sloans are done, and go way up when mortgage is done. Add in the 'known' salary increases. It's hard to put a set number.
Wish there was an only calculator where you change inputs yearly as I can reasonable guess my next ten years and know the variability in it.