John Deere 332G Skid Steer DEF Fluid Life Before Going Bad

2022 John Deere 332G Ser# 1T0332GMLNF414351 Machine at 450 HRS
Have only used my machine for 3 hours since last April 2023. DEF tank is 80% full. Does it need to be dumped out and changed or can it be topped up and run for a couple hours. What problems can it cause if too long and not burned. Maybe mg2361 or some other John Deere Guru can give their opinions.
Thanks Any opinions respected.
Simon C

I think the def has a 6-12 month life span depending on climate. One of the diesel mechs (I think) on this forum recommended I flush the tank out every 6 months with distilled water to clean it up. My 333g manual also says that using distilled water to flush out the system is fine. I
The problem with leaving it sit can be the it starts to crystalize and clog the system up. Thats also why I run my engine at 1/3 rpm or higher when I am working because not getting the engine hot enough can also cause the def to not properly inject into the system and it clogs stuff up too according to others on this forum.