How long before a PC becomes obsolete?

When it comes to the lifespan of a personal computer, how long can we realistically expect it to remain functional and up-to-date with the latest technology? With the rapid advancements in hardware and software, is there a definitive time frame before a PC becomes obsolete, or does it depend on individual usage and maintenance? Are there any key indicators or milestones that can help users anticipate when it might be time to upgrade to a newer model?