Preventative Maintenance - who needs it?

While speaking to a friend of mine on the phone the other day, who was asking where she could purchase media filters and how often they needed to be replaced,  I mentioned to her that Air Tech of  Houston has a Preventative Maintenance agreement, and the technicians will bring the filters with them at their scheduled services in the Spring and the Fall.
I was quite surprised to hear her say, "Oh, we don't need that. We just had the entire system replaced in 2009! And it has a 10 year warranty."
I felt the need to enlighten consumers of  the importance of Preventative Maintenance, whether your system is brand new, or even past its life expectancy.
You could have a limited warranty, an extended warranty, or the warranty may even already be expired. 
Proper maintenance is required if you want anything to operate at its peek performance. Including, your air conditioning and heating equipment.
Many people are concerned about what the warranty is, but don't take the time to review the terms and conditions of their warranty.
Manufacturers will stand behind their product if it is properly maintained, but negligence is abuse, and manufacturers will not reach into there pockets to replace a product that has been abused. Be sure to read and retain all documentation on your equipment. The manufacturer may also require documentation of proper maintenance be provided when filing a warranty claim.
And if your warranty is expired, that means you will have to foot the entire bill for repairs or replacement.
If you keep your equipment properly maintained, this will prevent costly breakdowns, increase the efficiency,  and you should be able to get a few extra years out of that system, even after your warranty has expired.
This message is for those of who spend $30 to change the oil on our vehicle as recommended, because they don't want to have to replace the engine for $2000. 
There are fortunate ones that have unlimited funds easily accessible for unexpected and costly replacement, that 'do not need' maintenance, they just need a salesman.