Here is the math:
55AH battery. A high quality battery decays at about 15-20% per year in available (AH) Amp hours. You need about 20% of initial AH left to start truck, if it starts quickly. Flasher/stop/turn bulbs are 25 watts each while parking lights are 3 watts each. Say you have two bulbs in front and 2 each on each rear light assembly for a total of 6 bulbs flashing. 25x6=150 watts 150 watts/12 volts=12.5 amps when they are lit. If they are only lit 50% of the time then you have an average of 6.25 amps. Now assuming you did NOT leave the ignition on or the parking lights on and the battery is fully charged and battery is only a year old. 55AHx80%=44ah Need 20% to start =11ah So you have 33AH left 33ah/6.25a = 5.3 hours till it will not start truck.Since you said you have replaced the battery twice lately either your alternator is not furnishing enough current or the battery voltage during charge is too low to fully charge the battery or you have a high constant drain of something left on discharging the battery.
Check the battery dra>Ok...lets talk about batteries since maybe this one is a turd.