Keep PPCG running in Game of Life
2986 2320 1228 generations
I wrote a rudimentary Python script for Golly to generate random 5x10 patterns until it encountered one whose population was fixed, and whose bounding box was not too large (as would be expected of soups containing spaceships, as spaceships expand the bounding box as they travel). Here was what it came up with after about 50,000 patterns investigated, and I suspect this is not maximal. If anyone wants to continue this search by using my script, it's located below the pattern.

RLE of solution:
# 2986 generations
x = 19, y = 20, rule = B3/S23
3o2b3o3b3o2b3o$o2bobo2bobo4bo$o2bobo2bobo4bo$3o2b3o2bo4bob2o$o4bo4bo4b
o2bo$o4bo5b3o2b2o5$7bobobo$7b2ob2o$8bo2bo$11bo$10b2o$7bo2bo2$8b4o$7bo$
7bo3bo!

Python script, to be run in Golly from File &gt; Run Script (not golfed). You will need to paste/draw in the PPCG pattern and select the 5x10 rectangle first.
import golly as g
from glife import rect, pattern

g.setrule(&quot;B3/S23&quot;) #set the rule to Conway's Life
soupcount = 0 #create a counter for # of soups processed

while True:
    pop = 0
    g.randfill(50) #randomly fill the 5x10 selection
    g.run(2400) #run the pattern for 2400 generations
    if g.getrect()[2] * g.getrect()[3] &lt; 40000: #after 2400 generations, if the bounding box is small
        pop = g.getpop() #check to make sure the population is not the same (pattern is not static)
        g.run(120)
        if g.getpop() != pop:
            g.run(9880) #after 9880 more generations, if the bounding box is still small
            if g.getrect()[2] * g.getrect()[3] &lt; 40000: #check to make sure the population is the same (pattern is static)
                pop = g.getpop()
                g.run(120)
                if g.getpop() == pop:
                    g.reset() #if so, break the loop and return the pattern
                    break
    g.reset() #repeat the loop and generate a new pattern if the pattern does not satisfy the conditions
    soupcount += 1
    g.show(str(soupcount)) #continually show the # of soups processed to make sure the program isn't dead

RLEs of old solutions:
#C 2320 generations
x = 19, y = 20, rule = B3/S23
3o2b3o3b3o2b3o$o2bobo2bobo4bo$o2bobo2bobo4bo$3o2b3o2bo4bob2o$o4bo4bo4b
o2bo$o4bo5b3o2b2o5$7bo3bo$7b3o$10bo2$7bo$7bo2bo$7bo$7b2o$7bo3bo$7b2o2b
o!

#C 1228 generations, found manually with Ctrl+5
#C to continually generate random 5x10 patterns
x = 19, y = 17, rule = B3/S23
3o2b3o3b3o2b3o$o2bobo2bobo4bo$o2bobo2bobo4bo$3o2b3o2bo4bob2o$o4bo4bo4b
o2bo$o4bo5b3o2b2o5$7b5o$7bobobo$7b2obo$8bob2o$8b4o$8bo2bo$7bobo!