I will give a quick rundown on a little of what I know about oils.
Perhaps by this means I can address this particular question of the wisdom of oiling before rather than during or after playing.
There are many kinds of oil, if we ignore vegetable oils found in cooking and drying oils found in timber preservation or artwork, we have several kinds of oil that fall under the umbrella of mineral oils.
The action of refining and the fractional distillation of mineral oils typically derived from crude oil, produces paraffins, olefins and white oils.
Olefins are in fact not themselves mineral oils but they are found in mineral oils.
All of these are hydrocarbons with various and different chemical bonds.
The refining of crude oil results in paraffins and white oils, both of which are suitable as a lubricant of an appropriate viscosity for use in lubricating brass instrument valves.
The problem is many manufacturers blend different oils to arrive at the precise viscosity they desire in their product. They also add various additives that control things like deterioration over time and corrosion.
What this means is a valve oil will probably contain additives and will consist of a mix or blend of light oils that each have different properties.
If these various additives and additional oils are not completely miscible (mixable) they can over a short period of time separate when standing.
Additionally the different light oils in the mix will very probably evaporate at different rates.
The result of this is leaving oil in an instrument over time such as for a day or two or longer may result in the mix breaking down and the properties of the mix changing.
The lightest fractions evaporate first and this typically means that over time the oil may become thicker and make the valves sluggish.
The purest oils, like double and triple refined white oils, or the most modern oils such as ultra pure, or the modern synthetic oils such as the excellent Yamaha oil, do not suffer from these issues.
In short the more you pay the better the product.
My opinion is synthetic oils such as the Yamaha product can be safely left in the instrument with an expectation that they will be unchanged and fit for purpose when you next come to play.
Changing to a different oil may hold issues when making a change. As a rule of thumb, the more expensive and the more pure the oil the better.
My own personal choice is blue juice. I consider it a good balance between performance and price. I have never had any issues with leaving blue juice on the valves for many days.
When it comes to choice of viscosity, the tighter the valves the thinner the oil should be. Yamaha valves are among the tightest in production and the Yamaha oil is a thin oil and is therefore the correct choice for these instruments.
So where we are is this, for most oils it is wiser to oil immediately before playing, whereas with the most modern synthetic oils such as the Yamaha oil, it will make no difference to the playability of the instrument if instead you oil at the end of playing.