The Hetman site is far from clear in the use/frequency of its oil range. Could you give us some indication of how often you should apply oil into the valve slides please ?
Personally, I only ever do it when they feel really gummed up. I oil the bearings and mechanical linkages on a weekly basis.
In general, oiling the valves after they begin to slow down is probably too late. Whatever is causing the valve to slow down is also working its evil against your valves. You need to keep ahead of the forces that work to damage your instrument, which has the added bonus effect of keeping your instrument playing well.
Here is an oiling regimen that I recommend, and it applies no matter which brand of lubricant you use.
Daily: When you are done playing, empty all the water. Remove the slides and oil each rotor with one drop of rotor oil on each side of the horn.
Weekly: Oil the bearings and any other moving contact points such as mechanical linkages with an oil formulated for bearings, one drop for each bearing point.
Monthly: Pull all the slides, wipe them clean with a paper towel, and apply a sparing amount of slide grease on the very ends before reinserting them.
Other tips related to lubricating the instrument
If your slides seem to “eat grease” and monthly is not sufficient for keeping them lubricated, then the slides may be loose. Have them checked and fixed.
If the slides “eat grease” and the rotors slow down, then you may be washing the slide grease away when you lubricate the rotors. Use a needle oiler and be sure to get the oil directly into the valve. Or, oil your rotors by putting the oil in the slide tubes and pushing them all the way in before rotating the horn to let the oil run into the valve. Use two drops per side of horn for this oiling method.
If you decide to change lubricants, ask your technician if the new lubricant will perform well with other lubricants you use. Some combinations will produce a gummy gel. Clean the valves before using a new lubricant.
Some technicians recommend oiling down the mouthpipe to help prevent corrosion. I recommend doing this every time you run the snake through the mouthpipe. Three to four drops of oil followed by a snaking will both remove deposits and oil the pipe. If you run water through your mouthpipe, oil first.