Your Stryd pod uses a lithium-ion battery. Lithium-ion batteries are great, and used in many devices such as phones, and have some limitations.
If you want to make yours last longer, here are some things to keep in mind:
Never leave your Stryd pod for multiple months without charging! Lithium-ion chemistry prefers partial discharge to deep discharge, so it's best to avoid taking the battery all the way down to zero. Since lithium-ion chemistry does not have a "memory", you do not harm the battery pack with a partial discharge. If the voltage of a lithium-ion cell drops below a certain level, it's ruined. You can avoid problems if you place your Stryd on the charger once it starts flashing.
Long-Term Storage of Stryd. Fully charge your Stryd and then do a hard reset* with the Stryd app on your phone. This will put Stryd in a mode where it cannot be accidentally activated and the power is switched off completely. Put Stryd in a drawer or on your shoe. Once you are ready to run, place Stryd on the charger to reactivate it.
Lithium-ion batteries age. They only last a limited number of years, even if they are sitting on a shelf unused. Do not "avoid using" the battery with the thought that the battery pack will last many more years. It won't. You can avoid problems if you place your Stryd on the charger once it starts flashing.
*Model 1 & 2 foot pods do not have the ability to Hard Reset via the Stryd app.
However, there is a workaround to do a hard reset of a Model 2 Stryd. If the battery is completely drained, Stryd will completely switch off and do a full restart. You can let the battery drain by itself, or you can expedite this process by simulating a run with your phone if it can still connect (connect your phone to your charger, start recording a run and wait). The battery of Stryd can last up to 20 hours. The LED will start blinking when the battery is low. You need to wait until the blinking of the LED stops, indicating there is no charge left. After the LED stops blinking, put Stryd back on the charger. It will restart and do a full reset.