While a good history of samples is really fine , a single sample can be a big help, as it could alert you to a disaster like anti freeze in the oil.
A decade of samples goes a long way in helping to sell a boat when the time comes.
*FF - TY for input... True on both counts!* Even though I feel*confident that both engines oil is currently in real good condition,*it will be interesting to learn actual PPM counts if/of any intrusions.* Interesting notion re decade of samples... re eventual sales as well as ongoing piece of mind.* You do that decade thing yourself?* I am fanatic in care of my mechanical systems on boats, cars, trucks... etc.* So much so that I virtually never take a vehicle out without checking all fluid levels and a gen visual survey.* I change fluids more often than most.* I learned early on that high-grade, clean, and full fluid counts in all sealed systems = best performance and mechanical longevity!* For joints, cables, interactive moving parts, springs and other items... WD40 is my friend!* **