99.9% of the time, paying with bitcoin goes through a payment processor such as bitpay, bitpay instantly sells your bitcoins for FIAT hence putting sell pressure on the market. So basically if people take your advice right now and start buying products with bitcoins, the price will fall.
I'm using Bitpay and Im not cashing it all out. My BTC goes into cold storage and at the end of the week I reconcile my bills and cash out only whats needed to cover those bills. Any BTC left over I keep! So, its not instant by any means, although I could set it up as such.
I also mine BTC and Im not cashing them out either.