With Iron Jetpacks once you go past Emerald tier you see lower actual "in flight" time.
This is calculated from the power storage/power usage
The below shows the time (in ticks) you can spend flying with each tier of jetpack

625 - Wood
1,428 - Stone
8,000 - Silver
32,258 - Electrum
33,333 - Gold
34,285 - Steel/Invar
46,153 - Diamond
50,000 - Platinum
54,545 - Emerald
43,636 - AllTheModium
45,283 - Vibranium
36,800 - Unobtanium

I guess it would make sense due to giving you more armor as you go higher tier? So the drawback is the flight time

The armor is op though lulz

i'd agree with the armor beign the reason you upgrade it.

also by time you could make this you likely could already be in end and with elytra.

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