Can you guarantee that i will earn daily at least 10$ with your method? If so, whats the updated price then?
Will it last for over years or just for a limited time only?
I can say that as of this moment, the accounts are netting about $10.7 per day and have been stable between $10-12 for the past 2 months but if there is a further market-wide crash, then you will earn less. There's obviously no guarantee when it comes to crypto. If tomorrow, the prices for steem crashed, you won't be able to earn the $10 but rather lesser. As you can see it started off with $100 a day last year but due to the crashes, it's at $10 at the moment.
The price of my bots and account however, will stay the same because it's a long term investment obviously as the accounts will be yours permanently and if you start now, you can break even with your investment in 4 months and the rest is pure profit. I made my first sale for $2000 actually and I have already brought the price down by A LOT to account for the bear market.
If you're unsure then I would suggest waiting another couple months to see how everything is going. I'm not going anywhere so no worries

If the crypto market can attain similar values as last year then I will obviously look into increasing the prices again as everything will be worth more. The only reason it's so cheap right now is because of the whole "4 months to break even" crap. Last year around this time it would have taken 20 days.
AND to answer your second question, it will definitely last over the years. Steemit has been around for almost 3 years now and it's still going strong and also has some of the highest number of transactions (
https://blocktivity.info/). If you follow their news, they're looking into creating SMTs as well which will allow easier ICOs per se which should hopefully increase it's price. If you're new to Steemit however, I would suggest creating an account and getting the hang of things before you purchase anything. You'll realize soon enough that this is actually a good opportunity for you

But for now, steem price relies heavily on BTC price (like 99% of other cryptos) and therefore, the price of steem is low due to the BTC price being low atm as well. Once the price rises, all of this will be worth A LOT more.