Is there anything that must be considered when purchasing larger stamp blocks?
Focus : Australian Stamps only.
Most large blocks, that are mute in the selvedge, I would not consider.
Used as yours, I would not entertain, (It may have the kangaroo flaws etc, but the overall look is poor)
1. Go by the best catalogue advice you have for blocks, Imprint blocks are collected, marginal markings, "traffic lights" etc.
2. blocks have a multi stamp design over the multiples, these can be valuable
Large blocks look good in an Album, providing they are mounted well and pristine.
Large blocks of mine, that have little $ value (but interest value)
This block however is valuable (see the green cross in the multiples)
End result, just collect what pleases you, be prudent in your purchases.