I don't think it is rational to put all your savings into BTC, but I do think it is rational to put a percentage of savings you are willing to lose into Bitcoin and see what happens, my thought is most of the Value in the BTC market cap is speculative.
I agree the economy is developing, but much slower than the market cap is increasing. I can't see the BTC - Fiat exchange stabilising, until all Bitcoin is evenly distributed.
(if BTC is a medium of exchange, then I should exchange it for something I preserve to be of equal value) The real value of BTC is in the technology (unquantifiable but everyone will benefit if we all use it) and some of the value is in the reduced fees, quantifiable, but not significant enough to warrant the risks of switching to BTC.
Though experiment: Now say I have BTC50,000 (I deserve it, I was an innovator/early adopter) the quantifiable value is: this is a medium of exchange, (fair enough, cool we can use it to exchange if I get you to believe it is good for tracking exchanges) it is +-1% more efficient that the existing system, and can't be inflated. (That is great this could be worth $1,000 a year to you. ) To realise that $1000 value, you will need to triad $100,000 worth of your material good and labour. I'll sell you 10BTC for $0.02, (you ask what I can buy with this, I say you need another 9,990 and you can buy a pizza.) Now somewhere around 10,000 people are interested in Bitcoin, and you get 1BTC for $13 if anyone of those people is to realise $1000 worth of benefit they have to invest $100,000 into the BTC economy, if all 10,000 members did that the BTC market cap would be worth $1,000,000,000, now we have BTC10,000,000 in existence today so my BTC50,000 will have a value of $5,000,000. The value I have provided is just $1,000 in efficiency over the existing system as an innovator/ early adopter. But I get to exchange as if I have provided 5,000 times that value.
My conclusion is 50 years of slavery to realise $1000 in value, (no way) the distribution of BTC is problematic. A disproportionate amount of wealth goes to too few for providing only marginal benefit. (a stable exchange rate only guarantees a disproportionate amount of wealth goes a few, while a crash with exstended periods of dispair may better distribute the BTC)
I see BTC 2.0 solving this problem, like the Americans solved the problem of England's gold monopoly by using silver. The distribution of BTC is worse that the gold monopoly problems leading up to the American war of independence. (to my recollection, the British had a virtual monopoly on gold, and required Americans to pay triad taxes in gold, hence the tea party).