My calc document takes over a minute (101 seconds) to load or save

I am wondering if there is a way to optimize the saving or to know how long each sheet takes to save so I could try to figure out what is the problem?
I save in the default .ods format. I tried saving in .xlsx format to see and it is much slower.
I am on Windows 8.1 and my computer is usually pretty fast (I4770 + 16GB ram + 4TB hard disk). I can copy this file 10 times and it is pretty much instantaneous on the disk drive.
The document is about 680Kb, it has ~90 sheets. It has no macro, barely any formatting, no comments, a few pictures, a lot of simple arithmetic math that recalculates instantly when I change a number, but there is quite a lot of text.
Sometimes I have to wait several seconds when inserting a row, other times it is fast.

I have the same problem: saving time for calc document is around 30 seconds. Document is ~200 K, has 2 sheets, ~ 100 macros (~ 6000 lines), 10 dialogs. Windows 10, LO 6.3.6.2. Computer is pretty fast. What should I do to decrease saving time?

You might try using sheet copy to move independent sheets to a new, fresh workbook then see how that saves, etc. What version of Calc? 90 sheets is really big. Is the little formatting you have for entire sheets, columns, or rows?

I have seen, in some spreadsheets sent to me, (unvoluntarily) pasted content until row 1048576.

Select all sheet tabs, select the last rows (or rows under the intended occupied rows), and look in the status bar for CountA: value.

In whatever sheet or in some specific ones?