Most batteries never see the end of the 4th year regardless of brand.

Quick and dirty troubleshooting check: hook up with jumper cables. Better = battery problem. Same = look elsewhere.

Have you checked obvious cable connections for tightness, corrosion, etc? Don't forget the ground to frame and hot to starter ends.

Most times you can tell by sound if it is cranking at proper RPMs but if voltage is weak your spark will suffer and cold temps won't help anything.

Jeff
96 T100 SR5 4WD Ext Cab, Warn Hubs, HD torsion bars, Bilsteins, Camper Shell, TJM bar, factory 31 x 10.5's, Powertrax No-slip rear, Recaro driver's bucket