I think the biggest gamble in keeping that machine would be the hard drive. It's been clocking up hours and start/stop cycles for 7 years now, and rotating drives always fail eventually. It might be tomorrow or 10 years from now, but the odds aren't going to get any better. At the very least, if you decide that there isn't anything available that suits your needs at your price, consider replacing the hard disk with an SSD.
I don't think you need to rush into anything, but I agree that it's probably time to start planning for a new computer.