Multiple autosave in nuke

So we had a little dataloss yesterday, some of our nuke files went 0B in size. Checked the autosaves... none existing! What happened (other than file system corrruption or what)? We are working on linux, and the NUKE_TEMP_DIR environment variable was properly set in init.py. But, nuke was started as a simple user, and that dir can be written only by root. At least this is my idea. That's about it, but I started to think where and how to place autosaves properly. We now having them in /home/user/Nuke/autosaves folder. Another question is how to preserve the autosave files? Because nuke deletes them as soon as the scene is saved, but we need them to stay, for these occasional dataloss events.
I found a tip in the mailing list, to include the current date, time in the autosaved filename:

/autosaves/[date %y]-[date %m]-[date %d]_[date %H]-[date %M]_[file tail [value root.name]]
But this is too long, and can get infinite number of autosaves.

So another tip: include only the current minute, so it starts again in the next hour, maximum of 60 file (for 1 scenefile, if you save a new version there can be another 60!)
[file rootname [value root.name]]-[date %M].nk.autosave
it gives path like (when for example the current time in minute is 15):
w:/Projects/Test/AutosaveTest/AutosaveTest_v001-15.nk
But that is still to much files.

How can it be reduced? I could include a modulo (%) operator to limit the number of minutes, like %6 gives only 0-5. It's great, but think. When minute is 01, it writes in the fileneme 01. When 02, 02 and so on, and when 06, it starts from the beginning. It would be better to have 1 autosave filename in the first 5 minutes (continuously overwritten), then another in the next 5 minutes, and so on. So in half an hour you still would have the first file, and that gives a good chance to go back if something went wrong. This can be achieved, by an expression like this:

[file rootname [value root.name]]-[expr int ([expr [date %M]%30]/5)].nk.autosave

Let's look at this from closer! The first part (before the "-") is simply gives back the file path, but without extension, so we can put anything after this. The second part can be understood from inside the date part: [date %M] is the minute of current time (That's going 0-59). Outside there is an expr(ession) command for the modulo (%30) operation, that gives the remaining of current minute and 30, with this we modified the range to 0-29. Then comes "/5", notice the brackets, so range is 0-5.8. Then the "expr int" takes only the integer of this. The final range is 0-5 integer only. This is pasted after the filename.
Now this expression makes a "filename-0" file when current minute is between 0-4, then "filename-1" when minutes 5-9... and at 30 it starts from the beginning, overwriting the "filename-0". There can be maximum of 6 files, for 1 version. But remember if you save the script (ctrl-s) the last autosave will be deleted!
I hope this will be useful for someone. Modify as you need.