The wallet needs to be loaded and unlocked for sprouting. The sprouting has a
minimum age limit of 6 hours before blocks can be sprouted. My observation
is there is a maximum age limit as well. I've reduced my oldest blocks
(ones with the largest number of confirmations) down to a month or two and
still those ones don't get used for sprouting.
Block sizes, I re-block all ones under 4k of Beans and depending on how
often you want to do it will determine the size you re-block them to. I
started re-blocking them to 16k which is fine if you have couple of million
but as your Bean bag gets bigger then this gets a tad of a pain in the butt.
I'm currently re-blocking mine to 100k+ now.
Re-blocking requires the coin control turned on and to save time, copy
your wallet address into both the destination address and the custom change
address. Mark the blocks you want and then put in half the amount of Beans
in the amount field. This has the advantage of producing two new blocks
of that amount. Saves time.
Conversely large blocks can be broken down into smaller ones using the same
process as more blocks gives you more opportunity to get one sprouting.
Best to lock the wallet before staring re-blocking as this can result in a
conflict with a block being selected and then subsequently being sprouted
before the transaction is confirmed.
Any happening like this can be reset by going into the console and
running checkwallet. If this reports errors then do a repairwallet.