Just wanted to pop in and comment on the length of her pvs on youtube and spotify... this is still pretty common especially with big Japanese labels (of which avex counts.) The Jpop industry is still very insular and does not court foreign markets like, say, Kpop does. Most of Japan's fans are still buying physical copies anyway, although sites like iTunes have become pretty big in the past few years.
Japan is pretty slow to catch up on these things. This is a country that still communicates via fax machines.
So, you don't see as much on streaming sites because they're only starting to experiment with them. PVs tend to be short because they want the domestic market to buy the DVDs, and most Jpop labels are NOT interested in marketing to overseas fans so they don't see much reason to make videos freely available (let alone in HD) or on worldwilde streaming services. It's only fairly recently we even get tracks on foreign itunes markets. Slowly but surely Jpop is sort of opening up to the world... but it's a very slow process. I think some labels are only now starting to see the market potential. (But this is a very kind of Japanese mindset... most people I talk to can't even believe anyone outside of Japan ((except for maybe Korea and China)) wants to listen to Jpop, watch Japanese dramas and movies, etc. It's not quite considered the exported product yet.
Ayu has always seemed very interested in foreign markets, though, and as her popularity and sales dwindle in Japan we kinda see her probing those other markets more.
She just joined up with avex's streaming site AWA so we'll see where that goes. I long for a day when (properly tagged, ugh, Kpop) Jpop is readily available on spotify and I can watch full HD videos on youtube! Or another video site THAT ISN'T REGION LOCKED BLARGH.