I'll drop this again as a reference for all folks joining DL and hoping for a quick upgrade.

Using the 'System-seniority-%-to-hold' is a much better way to forecast how long it'll take you to upgrade.

The ALPA website can show you predicted retirements to help you figure out how quickly your number will rise. Calculating how many are hired after you (needed for the total list size) is anyone's guess, and thus is the unknown/unknowable. Look at the analysis that Fangs has done and it'll give you the best data-driven estimate for "time to upgrade". Spoiler: no one can guarantee a 'time to upgrade'.

AE Trend Analysis thread