A "remodel" usually brings the effective age of your home down. A 30 year old home could "effectively" be 5-10 years old if enough updating is done.
If a remodel will include adding square footage, it is important not to make the home a super-improvement for the area. If the typical home in your neighborhood has 2,000 square feet of livable area, I would not go beyond 2,500-2,700 square feet of additions. If you enlarge to 4,000 square feet, you'll never come close to getting your money back.
Information we, Realtors, can give. However, you stated, "No Realtors until I decide I want to sell". So do you want to hear from us now or not? Your question / statement is just a little confusing.