To further support your decision, I had a wonderful pony that I got in my barn when he was 18. He was sound and useful up through his twenties and early 30s, retired at 33 and sadly passed at 35. So he gave me 15 rock solid, good years of teaching children to ride, showing, Pony Clubbing and fox hunting and then introducing my daughter to horses. He was beyond priceless and I couldn't have replaced him for any amount of money.
I so wish that every great pony could live out his days with an owner like you.
I have been fortunate and not been in that position with a horse, but I spent in excess of $6k with my dog, and only got another 6 months with him. Every second was worth every penny, and I'd spend it again in a heartbeat for just one extra day.