如果考慮持有到期，也許直接買 secondary market t-bond 比 TLT 更好

散戶買 secondary market t-bond

a) 買賣 minimum amount 比較大（今天在 Fidelity：2.875 5/15/2043 ask yield = 5.049, min 200K）

b) 要賣掉 bid-ask spread 大一點 (2.875 5/15/2043 bid-ask 73.053-73.127, TLT bid-ask spread 1 cent)

T 2.875 5/15/2043 modified duration ~= 13.7 year

TLT expense ratio ~= 0.15%, yield ~= 4.920, modified duration ~= 16.5

T 2.875 5/15/2043 is less risky and has better yield, has no expense ratio.  Larger bid-ask spread when you want to sell.