How Do You Know When It Is Time?

How do you know when it is time for a new bed?  Has it been 7 or 8 years since my last mattress purchase? Yeah, more like 25.  Do I have poor sleep quality?  Check.  I sleep just as well camping  on a yoga mat as I do in my bed which says a lot.  Also, when sleeping in my son's house in Bremerton, I sleep much better on his futon than I do on my bed.  Add that to  the fact that it's not good for me to take Tylenol or Aleve every night at bedtime to even get to sleep at all.  Do I have a lumpy mattress?  I don't think so but the box spring shows wear.  Is the frame unstable?  This brass bed of mine has been loud and squeaky from day one.  Just turning over in bed, as I do many times a night, creates a metallic ruckus.  I am tired of my squeaky bed!  The other reason for buying a new bed is that I picture the current dust mites in my bed as being the great, great, great, great, great, great, great, great, great to the tenth power grandchildren of the dust mites from my ex so that is totally nasty. I should have gotten a new bed a long time ago for that reason alone. So I bought a new bed.  The frame is wood and the furniture style is mission.  This bed is solid.  Once the stain is totally dry I will lug it up the stairs and put it together.  I hope I sleep well in it knowing any dust mites are mine, all mine.