Setting the tmp to random numbers won't help, if you know the bit flags for .tmp, you can do some fancy stuff.  

0x01 is whether it is a head or not.

0x02 is whether the tail does NOT get longer over time(Fixed in v80)

0x04 is wait flag, don't set this, it delays moving for one update

0x08 means particles never die (which is what this topic is about, fixed in v80)

0x10 means it is Dying and will glow until fadeout (although with the head flag it will still grow, and won't save this flag)

0x20 and 0x40 is direction of head

11th - 16th is the color. (0-31)<<11

.tmp2 is the tail length

If you want to make particles never die from a specific tron, create a tron particle and set its .tmp to 9 (1+8). It will be red, because the color was 0, to set a color, pick a number 0-31 and multiply it by 2048.  Try setting one to 32789(1+ 16*2048), it will be some purple color.