Older liquid yeast slow to start fermentation

I brewed a black IPA last weekend and due to time restraints, I decided to pitch a vial of WLP051 directly into primary at 64F (my basement temp and the same as fermentation temp). The yeast strain had an expiration date of May 31. 2013 (5 weeks away, but still near end of effectiveness range). Visible signs of fermentation took around 72-75 hours to appear. Should I be concerned with this delay in onset of fermentation? I do try to practice good sanitation practices, and the fermenter remained closed with airlock during the period.

My experience with liquid yeast is they drag their butt's and are slow to start if simply pitched and not used as a starter. Took 3-4 days before. I'm a dry yeast fan as they don't need their hand held as much and are much cheaper.

When you underpitch, you get a longer lag (which you just saw), you get increased ester production (undesirable in many styles), and you very possibly get lower attenuation (final gravity finishes higher than it otherwise would have).

If you are using liquid yeast, always make a starter.

+2 above. Always use a starter for liquid, unless its a sub 1.040 OG beer and you have fresh liquid yeast.

If you don't like making starters, than dry yeasts are your best bet. I was a "liquid with starter" only guy for a long time. I washed and reused. Lately I've made several with single packet of dry yeast (average gravity) and had excellent results too.

It doesn't matter if you use liquid or dry yeast what matters is the yeast cells per billion you need to ferment your wort. A starter helps you get your yeast to the needed cell count. Check out Mr. Malty or another Yeast Calculator online it takes all the guess work out of it. It also tells you how many vials or packets of yeast you will need if you don't want to make a starter.