Does this matter and is it better to send when a new block has just beenupdated?
Normally? No.
If the time gets excessively large, it could be a warning sign that there is a possibility of a split/fork in the blockchain.
If a block has actually occured significantly more recently, then it could be an indication that Bittrex is not communicating properly with the rest of the Bitcoin network.
I have noticed that fees are sometimes different, is it cheaper to send when a block has just updated?
It is cheaper to send when there have been less people than average sending transactions recently. The time since the last block is not an indicator of likely fees.
