Now all 4 years, most episodes on YouTube.
I watched the first season in 2011 on a now defunct site Joost. Been on the look out for remaining episodes since. Although badly organized, advertising interruptions and frustrating the obsessives this is quite a treat. Image quality is great. High production values, quality guest actors make the limited, repetitive stories entertaining. This access to a generous portion of episodes is enough for me.
Don't collect,access. You won't live long enough to watch all the stuff you already have.