The transmission was $10k. I don't have another $1k just lying around to further spend on this entire ordeal. I did ask them to flow test the current radiator and cooler lines to ensure no blockage.
If I have to shell out another $1k to protect my $10k investment, I'll have to figure it out, but I thought flow testing and flushing the current one was fine.
At 120k or so, its probably fine for now/short term but I'd prioritize its replacement within the next 30k or so. The main concern is the internal trans cooler leaking coolant under pressure into the trans. Just one drive cycle of this is sufficient to turn your new 10k trans/tc into a fancy, heavy transmission-shaped paper weight.
Like i always tell folks: cost+risk must be less than benefit.
If the benefit of radiator replacent in terms of cost avoidance (replacing trans again) combined with relative likelihood of failure in relevant timescales is less than the $1000 (cost) you'd have to spend to mitigate the risk of failure (which you deem to be low at this time), then wait.
If the spending the 1k to replace is more beneficial to you than the risk you're taking by not replacing it and having that risk realized when it fails, then invest the 1k to replace it now.
Ultimately, it's your call...