I think we have all been in this situation before. Devs fill TEMPDB then say they need more TEMPDB.
Here is my setup: I have a 4 node DW each with about a 1-1.5TB database living on them. My largest table is about 850GB in each. (1,440,695,540 rows, 353,312,408KB data, 510,599,720KB index (lol yea)).
My tempdb is setup like this:
8 5GB data files (so 40GB total tempdb data file space)
1 10GB log file
As a dba here is what I have always maintained: if your query takes more than 10GB of tempdb to run, the query and/or design is flawed. in this case I have given them 40GB data and 10GB log and yet they still manage to fill that from time to time with queries that run for hours. yes, the fill can be a stats issue. In either situation, imo, the solution is NOT to add more tempdb, but to fix the underlying problem w/ the query/stats.
So really discuss this and help chime in with your feedback on whether you think my logic is correct in that my file sizes are adequate and you should fix the root cause, or I should give in and give more tempdb space for what I viewed as flawed logic.