I am quite fed up with the instability of my /opt filesystem.
Every time I turn off my N900 I am not sure it will wake up well or with a damaged home partition, and always do a sync and wait until I see no cpu activity to turn off. But this seems not to help.

One of the most dangerous activities is changing the desktop theme: it more then often ends in uncountable errors in /opt.

I must thank Titan's power kernel for its forced fsck on start and RobbieThe1st backupmenu otherwise I would be forced to start over twice weekly, and this is becoming unbearable.

I thought it was swappolube, but the /opt filesystem seems to generate errors either with or without it.

What could I do to get more stability? Thanks in advance

Are there any messages from fsck? Sounds like a broken flash.
Ask Nokia support (if there is any) or go to Nokia Shop.

If it's a broken flash, then you should see block-level errors in the kernel log as well as filesystem errors.

Once you're sure the fs is correct (ie after a fsck), wait until it screws up again and post us a dmesg.

It does sound like hardware. Are you using Titan's kernel to undervolt? Maybe spend some time at stock speeds & voltage to rule that out.

Might be my undervolting scheme, right.
Yes, I didn't remind I were undervolting.
Going to give more millivolts to the thing, and see what happens. Thanks.

Remember that anything above stock speeds isn't guaranteed to be stable, even when you're pushing a higher voltage through it. While an OC might look stable (stable enough to not let apps crash), it can still corrupt your files when something goes wrong while writing to them.

You can always try a full reflash (including the eMMC image) as a last resort.

One of the most damaging things I ever did to the filesystem on my N900 was run fsck on it. It was otherwise working fine, but I was missing some free space. After fsck, it was totally messed up.

And yes, /home was unmounted when I ran fsck.

I ended up doing mkfs on it and restoring from backup.

I must say that running on kernel-power-46 with 250-600 MHz and stock voltages the thing seems much more stable. I miss the 1GHz feel but I am oh so tired of reflashing, so I'll stay with this until my fingers start itching again

Again, a simple experiment was enough to destroy my /optfs... and I was running power-kernel-46 at stock voltages and frequencies. I only tried to activate smartreflex while the n900 was stable, sync had been freshly executed, no apps apart from qcpufrequency and xterm were open.
Crash.
Reboot... opt filesystem borked. Two hours lost in restoring from backupmenu (of course backup wasn't going to work as expected - but at least I did it).

It's my fourth year with Maemo. I'm starting to be tired of it all. I hear the song of Android sirens... they sing of using it, not hacking it, and rest in peace...

I'm confused. Are you blaming Maemo for problems resulting from messing with your CPU voltages and clocks? This seems more like hardware issues causing unpredictable behavior, not Maemo being bad, since the ext3 driver is obviously not reacting well to your tweaks. Issues, mind you, not seen when the clocks and voltages are left alone.

Why use power kernel v46? 42 is the stable one, 99% of people who use the power kernel should be using v42 or below.