There are a few reasons why the caps blow in the first place. Overall, heat is the culprit, but there are a few factors to consider.
1. Physical size: The larger the can, the more heat it can dissipate.
2. ESR: Equivalent Series Resistance. The higher the ESR, the more power is lost as heat inside of the capacitor, needing to be shed by #1.
3. Electrolyte formula: Some electrolyte formulas withstand temperature better than others - both how high of temp, and for how *long* they can withstand that temp.
Keep in mind that as operating temperature goes down, the lifespan goes up HUGELY. So even if they're rated for a "measly" 3,000-7,000 hours @105C, if you're running them at sane temps, they will last exponentially longer. A combination of a large can, low ESR, and long-life electrolytic is what you're looking for.
If you want to do it right, throw something like some
Panasonic FM or
Nichicon HE capacitors in there, with preference to the Panasonics. Get the same diameter, same working voltage as the replacements, and at least as high of capacitance. In every monitor I've ever re-capped, I've had room to go at least one size taller on the replacement caps than the original units, which means both a larger can, and lower ESR. When you see a "bank" of capacitors of equal size, near each other, if even one is popped, REPLACE THEM ALL. Mouser or Digikey should have the Panasonic FM series.
If you follow those guidelines, the new caps will outlast the rest of the monitor. If you buy cheap caps (like those at Rat Shack), you'll be getting high ESR, and low-temp/low life electrolytes, and you may just end up doing it again before long. Your original caps failed because they were cheap, don't make the same mistake again.