the sound starts to fade after 2-3 seconds when i bend strings or hammer and pull off repeatedly

Heavier gauge strings
Raise your action and play harder (would slightly increase your sustain)
Practice vibrato for the purpose of increasing your sustain
adjust your pickup heights so they are closer to your strings (make sure you don't overdo it, and compromise tone)

btw this is a les paul

idk if there is anything to do for it

also are there any good vibrato excercises?

Well, heavier strings would definitely increase sustain, and is quite doable on any guitar. (though some may need adjustments to handle increased tension, but I wasn't suggesting you go out and buy the heaviest strings on the market either. Going up even just 1 gauge could help a lot with sustain)

And you can raise your action, but I'm not sure how difficult this would be, as I do not own a LP.
I don't really know any vibrato exercises off the top of my head though. Maybe someone else will be able to suggest some.

This post was edited by PSPZorZ on Jul 22 2010 09:03pm

You can add more mass to the headstock or the bridge of the guitar too. Denser bridge blocks increase sustain. I've heard of people adding a sort of weight to the headstock with noticeable results.

If you like really dirty sounds you can look into maybe getting a fuzz pedal too. Tonebenders and Big Muffs are renowned for sustain Muffs moreso than the Tonebenders. In fact, the gain knob on a traditional Big Muff is labeled Sustain.

This post was edited by Derkaderk on Jul 22 2010 10:56pm

you could just get a sustain pedal lol

Ha... obvious joke but a good suggestion none the less! Increasing mass is the way to go. Headstock and body (bridge) but yea, why not go for a compressor? This is my fav:



Very transparent. Prolly cheaper than modding your guitar and can be used on all your guitars!!!

MXR has a pretty similar comp for about $40 less too

http://proguitarshop.com/store/effects-compressor-pedals-c-87/mxr-custom-comp-csp202-p-1579

has 2 external knobs and 2 internal trimmers iirc. it's a good Compressor especially for the price

change your nut to brass instead of plastic for more, or could go all out and get a fernandes sustainer pick up, lil body work may be done installing it for switches and battery but you'll never have that problem agian, ever lol. or just put in high power or good humbuckers in, change your vol and tone pot for 500k or 1meg pots. get a Silver Mica Bleed Capacitor for your Volume Pot, orange drop 225p or higher power for your tone pod depending on vol and tone pot power.
add more gain or reverb to amp settings or get better amp, or eq pedal, or try TURNING IT UP to see any differents.

check your action, ( might be too low tht its touching the frets )
next check you neck.