Painting with Knifes

I've got three pretty ancient painting knives, plus a palette knife of more recent vintage: so I can vouch for Satu's opinion that they'll last forever - if they're well-made. Mine were all made, I think, by George Rowney (only one is stamped as such on the blade), so before the merger of the Daler Board Company with Rowney's - and that was a good few years ago. You can damage them, principally by dropping them on the flexible blade, and they can take on a bit of a twist, betraying whether you're right or left handed, but good ones will last for decades. How they stand up to really heavy wear, eg being used every day for ten years or more, I don't know - anyone? Got questions for those who use knives more than I do.... the painting knife and the palette knife aren't the same thing, the latter being much more rigid. But does anyone use a palette knife for actual painting? And, while I'm normally a fairly fanatical hater of all things Bob Ross (apart from his voice, which has sent me nodding off more than once) the Bob Ross company sells two painting knives which the man himself used: they're both wedge-shaped, with two facets, and I don't know how flexible they are - but they look like quite useful implements. Has anyone tried them for "normal" oil painting, ie the non-Bob techniques? I'd rather like to give them a try, but like most products of that company they're not especially cheap - opinions would be welcome.

Mr. Ross's knife is similar in shape to the Liquitex large knives 12 and 13...