I run the spare parts department for a major engineering (not aviation based) firm. Our stock control is managed by SysPro 6.0 - (shouldn't be too hard to search out the URL ..). SysPro is a vast and customisable networked business solution, it can handle the shelf life and GRN that you specified and a whole lot more (invoicing, warehousing, transacting, costing, kitting, backflushing etc and a whole host of accountancy functions). I also happen to know that it is ******* expensive! As it also handles the entire company’s accounts it may have too great a scope for what you require, but it may be worth contacting them with your requirements; they may be able to provide a version that suits.
The engineering side of the company is catered for by Pulse. I know that Pulse has some inventory control modules but we don't use them so I cant really comment on their suitability, but I do know that is has better implementation of ECR's, ECO's revision numbers etc than SysPro. I don't have a web address to hand but if you're interested I can find out.
WD