Yes, you are right, knowing the clock rate and duty cycle would be interesting to know. And knowing what the MCU is actually doing. Powering an MCU from a lemon or potato is nothing new and has been done with more than 30 year old MCU's, implementing clock's etc.
More challenging is probably to power a complete system, i.e. everything around the MCU, like driving Ethernet or WiFi or BT as well as some analog sensors and the like. Embedded MCU's do not require much and if you can spread out the computing needs over time, no big deal.
Look at Casio watches and the like which you can run for 10 years and they provide quite some features. It's okay as long as it is features that stay within the MCU/Display realm. Now, the watches which provide BT, GPS, different sensors etc kind of suck in this regard.
More challenging is probably to power a complete system, i.e. everything around the MCU, like driving Ethernet or WiFi or BT as well as some analog sensors and the like. Embedded MCU's do not require much and if you can spread out the computing needs over time, no big deal.
Look at Casio watches and the like which you can run for 10 years and they provide quite some features. It's okay as long as it is features that stay within the MCU/Display realm. Now, the watches which provide BT, GPS, different sensors etc kind of suck in this regard.