No, other than perhaps to get upgraded features such as moisture-sensing autodry if your current machine doesn't have it, or larger capacity if that'd be useful to you. Autodry doesn't make the machine directly more efficient, it just helps eliminate guesswork in setting drying time ... but after 25 years, you probably have a good handle on how long it takes to dry your typical loads.

Just clean inside periodically to remove lint/dust and keep the vents clean. Otherwise, keep it going. The link below shows how to remove the drum and then clean a dryer for various models.

Here is a link that might be useful: Dryer Repair Tutorials

My Maytag DG712 would have been 25+ years old by now and many of its operating features are still used today. Components today may be less reliable than those used in that early machine but the Neptune dryer I have been using the past 10 years has a couple nice features like a much easier access to the laundry the way the opening is cut into the cabinet and the door is part of the cabinet as a result. Touchscreen programmable loads is another great feature you couldnt have had back then. But functionally the major components are essentially the same.

Are there any reasons to replace a 25 year old dryer that still works well?
No, and in my opinion, it may even outlast something that you would buy new. My Maytag (propane) gas dryer is probably 25-30 years old, going strong and I wouldn't dream of replacing it. About 5 years ago it wasn't igniting/heating properly, but the fix was quite inexpensive....small local repair shop that did not charge an arm and a leg.