You want your money to be as safe as possible, that is the #1 criteria.
It doesn't matter how long the book is in business. All that matters is what practices they are taking to protect users funds.
Bitbook was considered by many the most trusted Bitcoin sportsbook, it was their slogan and they never failed to pay a winning bet. Yet one day they too disappeared without paying all their customers.
You might argue that the more time the book is in business, the less chance there is for them to disappear. But on the other hand, the more time the book is in business, the more customers they have, the more deposits they hold, the more incentive for them to steal it and disappear.
Take for example Full Tilt Poker. They were the second largest on-line poker room for a decade, endorsed by dozens of top players, you would have rated them AAA+++ and players felt confident to keep there millions, yet they too stole hundreds of millions dollars from players deposits and had Poker Stars not buy them out, most of that money would have been gone. Same for Ultimate Bet, Absolute Poker, all top on-line poker rooms at the time with the exception Poker Stars.
If security is your concern, for rating purposes, you should dig deeper into what is done to protect users funds.For your Bitcoins to be safe in a sportsbook account, the sportsbook needs to store all user-owned Bitcoins (deposits and winnings) in a separate account from the account used to pay for their daily operations, in a similar way that Poker Stars is doing for its Poker players. In addition, it needs to make sure that there is always more than enough funds in the segregated account to cover all user balances in the event that everyone will want to withdrawal their entire balances at the same time.
Furthermore, they need to prove that they control the Bitcoins in the segregated account, and allow an independent 3rd party to audit it at any time.
Finally, they need to demonstrate that access to the cold storage of Bitcoins is not limited to one or two persons, otherwise, in the unfortunate event that something terrible happens to them, the Bitcoins will be gone. For this reason, the sportsbooks need to provide a 3rd independent and trusted escrow service with an access to the segregated Bitcoins that are used to cover user balances, and an authorization to distribute them to their owners in unfortunate circumstances.
To the best of my knowledge, none of the Bitcoin sportsbooks follow this practice or a similar one, and therefore your Bitcoins are not safe in any of them, regardless of how long they are in business.
Stating that they have the Bitcoins in a cold storage is meaningless. They need to prove it, they need to allow an independent 3rd party to audit it at any time, and they need to show how you will get your Bitcoins in the unfortunate event that the people in control of it die.
Recently, there have been many Bitcoin sportsbooks that disappeared with all user balances. Unfortunately, as history has learned us, this will continue as long as there is no true protection to the users, similar to the one provided by Poker Stars in the poker industry.
Why DirectBet is the safest Bitcoin Sportsbook ?We are the safest Bitcoin sportsbook for the simple reason that we do not take deposits and keep hold of your valuable Bitcoins, except during the lifetime of the bet and only the amount that you elected to bet. This period of time is kept to the minimum thanks to the fact that we settle all bets within an hour. Your Bitcoins are kept safe in your wallet under your control at all other times.
We are different than other Bitcoin sportbooks, who take deposits and keep hold of your Bitcoins for no good reason. By doing so, your Bitcoins are left vulnerable to theft or loss, and there is always the risk that the sportsbook will disappear, taking your Bitcoins along the way, or spend them on their operational costs, or use them to pay winning players, essentially turning into a Ponzi scheme, or otherwise prevent you from withdrawing for various dishonest reasons, as happened countless of times in the past.
In fact, to date, there hasn't been a single Bitcoin sportsbook that we are aware of, which ceased operation gracefylly and honored all withdrawal requests.
Currently, none of the other Bitcoin sportbooks take the necessary steps to truly protect deposits in a similar way that Poker Stars is doing in the on-line Poker industry for its Poker players, and therefore your Bitcoins are not safe in any of them.