Update 4:
Hi everybody, it's been a while. Unfortunately, when starting this experiment, I completely forgot about an upcoming business trip, and it consumed the entire week. Not only was I unable to write updates, but I also couldn't fully follow my experiment. But first things first.
After the first 10 days, my average price was 2642 sats for a Euro. Now it's 2247 on the market, meaning it was cheaper this month to rely on credit than to buy on the spot when needed. Buying gift cards, I was spending almost 400 sats per Euro more than if I lived on credit and paid it off after 10 days.
Mostly, I was using Bitcoin for gift cards for groceries and car fuel, which is quite seamless. However, with big gift cards, you need to keep track of a balance, so it's quite cumbersome. I had just two native Bitcoin purchases: buying merchandise in a shop and a VPN.
Bottom line - if your life isn't slow and planned in advance, you cannot rely on spot Bitcoin purchases for gift cards at the moment. Gift cards are helpful but cannot replace normal life, especially when you make spontaneous purchases like I did during the business trip. When you're running between meetings or have an hour before a flight to buy souvenirs, you don't really have time to research the area and buy local gift cards.
I think I forgot how easy and convenient the current payment system is. I need Apple Pay integration for lightning payments, or a debit card that you can instantly top up with lightning, or native adoption. Intermediary solutions are good when you have time to use them.
Next phase - I'll live on credit and cover it later on the payment day, as Jack suggests in the original video.