Should work. o_O Setting with an absurdly number will wrap around to a small number if it exceeds 65536 in some cases. Setting zero makes them not die, ever. Newly generated ones however, less so.
The max life when you save is 50.000 The max speed of a spng XD is 10
If you put !set life XXXX 1000000000 when you reload the sim its down to 50.000 or minus... !set vx (or vy) XXXX 11 ... when you reload it downs to 10 Etc....