I have had long running saved searches fail to export as Excel, but I was able to get them to export them as CSV files. It's worth trying. I think it takes longer to produce the Excel files, and it may time out under certain conditions.

@scottvonduhn thanks for that tip, I was able to get that search via CSV

Great! Glad to know it worked for you.

Another thought on this maybe to set a schedule on that search to run and email the results to you when completed. It is able to execute much more process intensive searches that way.

Not certain if this was mentioned, but don't forget about the Persist (CSV) option that can be found under Reports => Saved Searches => All Saved Searches. We often have to use this for searches that return over 900k rows of results. Only option is CSV (ie no Excel) but it runs in the background and has worked every time.