The stator generates voltage and the voltage is the push behind the amperage - the rectifier changes the AC voltage of the generator into DC voltage to supply the electrical system (lights, winch, AWD magnet coil and stereo, gps, cell phone?) - the regulator has to provide enough amperage to run all the add on's and 1.5 amps to charge the battery. What amperage was the system designed to supply and how does the rectifier/regulator dissipate the heat (watts) generated by the load on the battery? Most rec/reg's fail from excessive heat either from abnormally high current draw or failure to shed the heat and ultimately a combination of both. What mods (if any) have increased the current demand of the electrical system? High wattage lights? Additional lights? Even LED's draw current and HID lights draw more than either incandescent or LED (in most cases, but it depends on the lights and the input current of the device.
Keep in mind, that as voltage decreases, amperage increases. To get 60 watts of illumination from a light bulb requires 5 amps at 12 volts - the same amount of light at 6 volts requires 10 amps of current - as the battery voltage drops, the charging system is taxed with supplying additional amperage to supply the wattage hungry accessories.
Survey your vehicle and estimate the amount of amperage required to operate all the equipment without consideration of charging the battery. How many amps does the fuel pump, fuel gauge, speedometer, headlight (on high beam), tail light, brake light (both on at the same time), dash lights, clock, clearance lights, ground effects lights, cell phone charger, GPS power supply, radio, stereo, CB radio, heated grips, thumb warmer, work light, spot light what ever you have that is normally on at the same time even if only for one day or a portion of a day. The diodes or MOSFET (metal-oxide semiconductor field-effect transistor which operates the same as a diode) is what normally fails and heat is the killer. The device can open like a fuse or short out and become a simple conductor.
Either reduce the draw or cool the unit more effectively