Three of these settings control the "heartbeat" of all particle displays, 三个控制“心脏跳动”的粒子效果显示
(the fourth setting is described seperately below.)

PSYS_SRC_BURST_COUNT:  the number of particles created per burst
PSYS_SRC_BURST_RATE:  the delay in seconds between each burst
PSYS_PART_MAX_AGE:  The # of seconds each particle lives, (up to 30)

You can accidentally create more rendering lag with these three settings than ALL the other particle settings combined.

The default maximum number of particles is 4096.  (that's from all emitters inside of a player's draw distance, not per emitter!).   When emitters try to create more than 4096 particles all at the same time, the result turns ugly.  Big gaps, faint displays, really slow computer performance, and emitter failure results.

You can't control the number of particles being displayed nearby, so it's up to you to make sure that your particle display 'plays well with others'.  This means sharing... and not trying to hog all 4096 particles to yourself.

10 particles per burst,
each living for 10 seconds
with  bursts every tenth (0.1th) of a second = 1000 particles.

You can calculate how many particles your emitter is responsible with this formula:

       ( age / rate ) * count
      
Even just one emitter can use up all 4096 particles, creating 1 at a time at a burst rate of 0.01, if the particles live for 40.96 seconds.

Using a burst rate of 0.00 is not recommended unless count = 1 and the age for the particles is 5 seconds or less.

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PSYS_SRC_MAX_AGE
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This setting says how many seconds to wait before turning the emitter off.  0 = never shut off.
The maximum is 60 seconds.  Sometimes it's better to turn particles off completely rather than use this to shut them off.

If this setting is not 0, the shut-off count-down is restarted everytime the prim is rezzed.   If you fly away and come back it starts over for you, (but not for the other people near the emitter that didn't leave!).  If you are wearing it and cross a sim boundary, the count-down starts over too.