Why the hell you think that you'll ever notice a difference in battery life span if you actually really only charge it to 90%? That's as much as true as it being wrong. You should start reading real books made of paper instead of reading the internetz-for-randoms, srsly.
Look it that way, your battery life span in dependant way more on how the battery is drained/charged, than to how much of its capacity in being recharged.You need to use that very same battery for at least 10 years to actually see a difference in life span, due to charging it to 90% instead of 100%....... and then again, you'll need a vast sample of batteries in lab conditions to even be able to tell if the difference is actually caused by this or that.
Use your battery as a normal user, it will last you probably more than you'll actually will own your moto g.
Also the phone charging circuitry limits the current to ~200mA/h after the battery is charged up to 90%.