Pet insurance is only available because the insurance company, after covering the vets fees, admin costs and overheads can still make a profit. Which basically means on average customers will pay a lot more in than they get out.
I’ve got 2 Jack Russells without insurance. The 14 year old is very ill, had a night in the vets last week along with scans and blood tests for £389 plus on going treatment on the other hand the 7 year old has cost £18 in those seven years. I’m happy to take my chances rather than paying for yet another policy that I might never use.
To answer the OPs question, start underwriting now. Set up a standing order to transfer the insurance premium into another account and dip in when you need it, if it builds up to an excessive amount take a payment holiday… not an option with insurance!
I don’t mean to get on my high horse here but for me the question of “worth it” will never be a financial one, it will be based on what is best for my dog(s).