No, we cannot guarantee that because of the variables involved.
Also, eBay sometimes add steps to the sign in process, normally for newer eBay members or members with few feedback. The extra steps prevent hidbid from signing in for you, preventing your snipe from being submitted.
Lastly, you may not meet the bidder requirements set by the seller of the item. This is the most common reason scheduled snipes do not execute.
To prevent these last two situations from arising, you can enter in a bid for the item on eBay, and then click the "Place Bid" button. Your bid will not be submitted because you'll have to click a "confirmed bid" button on the next page.