Is it OK if I buy a Sightstone if I'm on mid lane?

According to my calculations if I place 2 wards every 3 minutes I'll get my money back in 15 minutes. After that it is a huge win to have the item. In most games I won't fill up my inventory or if I do it will be well over the 30 minute mark.

So is it viable to buy this item on any other role than a support? (I'm assuming that the support player also buys it.)

Overall, I believe it's a bad idea. Some things to consider:

• A Sightstone costs a lot of money up front. In fact, you can't buy it at the start of the game, unlike a ward or 2. That means you will be without any wards for several minutes at least, when you are most vulnerable to ganks, and a death because of that will cost you much more gold than you saved. Also, if you leave the lane early to complete the Sightstone, you may miss cs because your opponent is still in lane and could push the wave into your tower while you buy.

• You forfeit AP/mana items in favor of a little survivability. You may not have enough damage to win trades, in which case a couple more hit points won't matter. Getting zoned out for a few minutes or outright killed because you can't deal enough trade damage will again cost you much more gold than you save.

• Do you really need 2 perma-wards? That means you push hard all the time and/or you prefer champions that are slow and lack non-ultimate escapes. Consider whether 1 ward per 3 minutes could be enough. Ward 1 side of the river and position yourself closer to that ward rather than the middle of the lane. That way, you have enough vision in either direction to run away from ganks.

In conclusion, smarter play and map awareness will dramatically reduce your need for wards. I do not believe a Sightstone is a viable item choice for carries, AP or AD.

Assuming you place enough wards during the game to make it worth and you can afford to lose tempo it should be a good item.

The drawbacks of this is that Sighstone is pretty expensive to buy at first. It only provide 180 health points for 950g. This will hinder your power compared to a champion going for a more offensive item.

However, sometimes power is not everything. If you (and the team) can take advantage of map awareness for a better play, this will be really worth. However, if you can't take advantage of a better warding, this will more prevent you from getting strong enough to win.

If you are already playing defensively and need a better protection against ganks, this can also be a good shot.