AIUI, Texas Instruments' MSP430 series[0] (which are 16-bit) is still king at low power.
Sleep modes bring that down below 50uA.
So on 2x AA batteries (~3000 mA-hours), it seems like these datasheets are telling me that all these chips can consistently hit 2.5 _YEARS_ of battery life? Or 6.5+ _YEARS_ of sleep-battery life?
I'm surprised at how low power modern microcontrollers are. The power-consumption metrics continue to get better-and-better year over year.
https://www.mouser.com/ProductDetail/Tadiran-Batteries/TL593...
0. https://www.edn.com/ti-msp430-mcu-breaks-500-nano-amp-barrie...
Some of the new AVR series are, however. A few of these have some of the same features offered in these Tinys (e.g., 12-bit differential ADCs)
SOIC would have been completely inaccessible for me as I mostly relied on breadboards and a radio shack soldering iron with a half-corroded tip that would probably be better suited for plumbing than placing SOICs
The actual soldering with surface-mount stuff does not mean you have to be like an industrial robot in your precision and gently apply heat to each tiny tiny leg, while also getting the solder in there just in time, all the while holding your breath so you don't blow things away. Not at all.
Surface-mount soldering can be done using way "uglier" techniques than through-hole, where you basically flood the component's legs with solder, heat it enough for it to melt and flow, and then remove the excess. Thanks to the magic of surface tension (and, if you have it, extra flux) the solder will flow to where you want it, all on its own. This kind of technique probably wouldn't cut it for production, where consistency and quality of course are important, but for hobby use it's fine!
There are plenty of YouTube videos showing this off, it can be really really easy. Please don't fear surface-mount soldering. Grab (the cool side of) your iron and join the fun!
But for a 15 year old with no budget and limited tooling (even flux would have been a luxury), being able to order off a sample form and get something that just worked was invaluable.
On the bright side, some SMD packages are still reasonably workable with a soldering iron, like SOIC, and cheap devboards that do little else than breakout into a DIP package are commonplace.