This last week I've been in the process of syncing my wallet to the Ethereum blockchain. I found one of the major setbacks I faced was the overall size of the blockchain when syncing onto my Macbook Air. I initially started syncing using the Mist Browser but soon found that it had already used more than 20gb to completely sync the blockchain, it was well over what I had available on my computer and it quickly caused problems.
In the end it took me 3 days on and off to completely sync the main-net and my laptop had already begun to overheat, I assume this is because it is an old laptop. It was then I was told about another wallet, Parity, which synced to the blockchain in about 2hours and only taking up about 11 or so GB.
Basically the Ethereum blockchain will gradually grow over time, so for those new to cryptocurrency ensure you have enough space on your hard drive disk when syncing your wallets.