Thanks for the feed back, keep the questions coming!

Kevin, before I answer I need to have more information, such as vehicle type, operations type, and oil (as not all oils are the same) Without this extra information I would stay with a conservative number of 300 hrs

Extending oil drains on the engine is quite complex, and should only be done in conjunction with a used oil analysis programme. This is the only way to establish if the engines and oil combination will allow extended service intervals to be run in your conditions.
We have a lot of success of running upto double OE drains using out semi-synthetic fluid castrol Hypuron, however the type of fluid (mineral or synthetic) is not the only determining factor for drain intervals.

operatig your equipent at lower temperatures it is often neccesary to drain out the summer (high viscosity) hydraulic fluid, and refill with a low viscosity winter fluid. However a better approach may be to use Castrol dual range, a multi grade hydraulic fluid that should be able to cope with some of the most extreme temperatures.

It is always the best approach to speak to the manufacturer of the equipment if using fuels that do not comply to the original reccommendations. Sulfur is a natural lubricant, and reducing the sulfur in fuel can create issue on some older equipment, however if you use a high quality fuel, not the cheapest you can find, it will have suplementary wear additives to compensate for the reduced sulfur.
Bio fuel is another matter all together, and studies are being conducted to establish the effects of using bio fuel with mixed results, however one thing is clear, if using bio fuel ensure it is of a consistant quality, and from a reputable source, as damage from poor fuel can be expensive and irreversible.
Again it is worth checking with the manufacturer of your equipment, but it appears that B5 (5% bio in diesel) can be used on most equipment.

cleaning of spills, is dificult especially if the pavement is made of asphalt, as any strong detergents can affect the strength of the asphalt.
For spills the most important thing to do is to contain the spill and then mop up the excess. Then using a water based detergent like Castrol super clean scrub the area with a brush, and plenty of water.