1 1/2 years sounds about right for an average laptop battery. In fact, depending on what cells were used, some are only designed to last 1 year tops. I know this sounds low, but the trend lately, has been to reduce capacity and service life in favor of flashy low prices.
For example, here is a
Inspiron N5010 battery that uses very high quality cells from Panasonic that deliver extra power and are designed to last a long time.
(In case the embedded link doesn't work here is the direct URL http
/www.safebatteries.com/inspiron-n5010-battery-black-5800mah.html)
This 6 cell Inspirion N5010 battery is built using much more expensive Panasonic NNP cells to rate at 5800mAh/62 Wh and and should last much longer in therms of service life.
Unfortunately, most after market laptop battery sellers don't sell batteries designed to last that long and/or provide less power then the original in many cases (A.K.A 4400mAh batteries)
It really does depend on the the type of cells that were used. If they spent .50 cents per cell then you are going to hate the battery, if the spent $7-$8 per cell then the performance will meet your expectations or perhaps exceed them.