When I use my m14x I usually have it resting on my thighs/stomach while I'm laying on my bed, it tends to get reasonably hot when I'm gaming but I've never actually check my temps . I do make sure to keep the fans clear, there are two at the bottom and one at the back. The ones at the bottom are on either side of my leg generally while the one at the back is clear. Is this ok to do? I suppose the only way of knowing for sure is checking the temps which I will do but I just want to know whether continuously running at seemingly high temps, although never actually seeing any effects (eg shut downs) could have damaged my system? How would I know if it has been damaged?
Well, I'd start off by actually checking temps. A general rule of thumb for temperatures is that when idling, the temps shouldn't exceed 60C (65C in certain cases). And while doing intensive operations/gaming- anything over 90C is getting toasty.
Your laptop is going to kick out a bit of heat- you can't avoid it, but nevertheless- you can do things to help cool the laptop down, such as investing in a laptop cooler, or spraying out the fans at least once a month with compressed air.
You won't likely damage your system, normally the reason why your computer might have an emergency shut down is to AVOID damaging it. But the heat can affect the life time of the components- so if you need the m14x to last, I'd keep up with the maintenance, try using a fan, or a flat object like a tall book to set under it when you game on your thighs/stomach.
Download CPUID hardware monitor. It will show your temps. Also, use a laptop cooler and contact alienware support@1-800-ALIENWARE. They can flash the BIOS for you. If you do it and brick your machine say goodbye 'cause they wont cover it even if under warranty, if they brick it they replace it if under waranty.
Thee have been heat issues surrounding the 14xr2, I have heard that a BIOS update can solve the issue but if not sometimes they replace the whole thing.
High-end laptops are now designed to be able to handle higher temps than in the past. For info related to your components look them up individually on he manufacturers websites.