You make a good point on 30 yr fixed early in th cycle. From a risk perspective it makes sense to go shorter which is the approach NLY chose. The question is when does AGNC start to unwind the 30 yr debt and move into shorter terms? By the way, 10 yr. treasury was down today so we can expect higher 30 yr. rates.
And why would it appreciate? It's not like anyone's going to buy the company. It doesn't make sense to have a firm like this that doesn't trade publicly.
The price is a reflection of the value of the dividend, balanced against the risk that the whole business model will be quenched by a change in the mortgage market or the fed's lending rates.
The total return is well in excess of the market average. That ought to be good enough for anyone. If you want compounding, just tell your broker to buy shares with the dividends. A do-it-yourself DRIP, if you like. Much better for the price to remain stable in that case.