@mara:
when booting from mmc, after some time of operation, the system crashes (ex: hildon-desktop restarts; processes automatically die...). Sometimes, a reboot helps; but after about 1-2 weeks of SD card usage, it cannot boot from it anymore
My last card lost the ability to "read sector 0", and became garbage since I can't even format it anymore.

I'm trying to understand what caused this.

Ilia

The most common trouble with cold is condensation: Bring a cold device indoors, and before you know it there will be water condensing on outside- as well as on inside surfaces and components. That may (nay, _will_) lead to electrical problems.

It almost sound like SD card internal wear leveling is not working... are the memory cards you are using "known good brand"?

52C isn't that bad under heavy load. My MacBook can hit 85C when I'm copying a DVD, running SETI@Home, etc.

Just a warning about battery life at the extremes of temperature.

excellent resource here: http://en.wikipedia.org/wiki/Lithium...ure_and_charge

The salient point is that operating temperature has a huge effect on battery life.

Some general points on prolonging your Li-Ion battery (C&P'ed from that site)

Guidelines for prolonging Li-ion battery life

* Unlike Ni-Cd batteries, lithium-ion batteries should be charged early and often. However, if they are not used for a long time, they should be brought to a charge level of around 40% - 60%. Lithium-ion batteries should not be frequently fully discharged and recharged ("deep-cycled") like Ni-Cd batteries, but this is necessary after about every 30th recharge to recalibrate any external electronic "fuel gauge" (e.g. State Of Charge meter). This prevents the fuel gauge from showing an incorrect battery charge.[14]
* Lithium-ion batteries should never be depleted to below their minimum voltage, 2.4v to 3.0v per cell.
* Li-ion batteries should be kept cool. Ideally they are stored in a refrigerator. Aging will take its toll much faster at high temperatures. The high temperatures found in cars cause lithium-ion batteries to degrade rapidly.
* According to one book,[34] lithium-ion batteries should not be frozen (most lithium-ion battery electrolytes freeze at approximately −40 °C; however, this is much colder than the lowest temperature reached by household freezers).
* Li-ion batteries should be bought only when needed, because the aging process begins as soon as the battery is manufactured.[14]
* When using a notebook computer running from fixed line power over extended periods, the battery should be removed,[35] and stored in a cool place so that it is not affected by the heat produced by the computer.

The list is good. Except for the point about recalibration by deep-cycling every 30th charge - I'm pretty certain this is only true for laptop batteries (with their stacked battery cells), NIT-type devices use, as far as I know, just a simple voltage meter to deduce the charge level. For the record, I've had my N800 for 13 months now and the battery meter behaves exactly as it used to 13 months ago (it's been fully discharged three or four times only by accident, and the last time was some 5 months ago).