To the OP, no reason not to... if they fit your charging system.
One example, for an alternator that charges at 60a or less, is the
ETX680: 4.1 lb, 12.4aH LiFePO4 for $379.
From this
discussion:
"First off, what's the amperage output from your alternator? If you're using a 60 amp alternator, you'll be OK with the ETX680 (but the ETX900 is fine). If you're using a stronger alternator like a 70 amp, you need the ETX900.
A basic rule of thumb for the ETX series: The first two digits on the battery model should be larger than the alternator's amperage.
Examples:
For a 60 amp alternator, use the ETX68(0).
For a 70 amp alternator, use the ETX90(0).