I never carry the fob unless I intend to valet.
Mobile key had been extremely reliable for me about 97% of the time. I recently had the antenna at the rear of the car replaced and it seems to have made it 100% reliable. Judging from posts here on the forum, iPhone mobile key seems to be much more reliable and simpler to use than android. Another good reason to visit your local Apple Store.
The fob suffers a problem with battery voltage. This is especially true if the battery has had “bitterant” applied to it. For more information on that, consult the FAQ at
www.lucidupdates.com. The bottom line is, make sure you wipe any such battery with alcohol thoroughly before putting it in the key. if the battery is even slightly below desirable voltage, the fob can begin to fail. This isn’t only true of our fob, apparently the same problem can occur other electronics, like Apple AirTags.
Fob schmob.