Do hps lamps get weaker over time?

Ive been growing indoors using hps for my flower room for about 2 years and I have noticed that my ladies are taking longer to mature than they should. Can this be caused by my hps lamps wimping out on me? How often do you change out your lamps? or do you?

The delayed maturation could be caused by other issues I am sure. Temps, etc. And I am trying to eliminate as many variables as I can, so any input would be appreciated.

What brought this to bear was a run of Blue Dream that I have just started to harvest.
Blue dream is supposed to be a 10 week strain, but my trichs didn't start showing amber until week 20!!!! I noticed that on my last run of white widow that it also was running longer than my previous run by about 3 weeks.

I flower in an 8 ft. x 8 ft. area with (4) 400 watt hps lamps in soil ( foxFarm O.F. )
My temps tend to fluctuate with the weather as it is in a shed that is hard to keep the temps correct, so I have had lows in the 60's in the winter and highs in the upper 80's in the summer.

Thanks for any advice in advance, this has got me quite stumped

mate i change my bulb every two grows just somethink i was told to do so i do it

Yeah, Most likely the bulb. Only thing I could think of, or a light leak. double check that too.

Change that bulb. Most HPS lights come with the recommendation that you change them at least once a year, because of performance decrease. For a pretty decent light, once a year is enough. But no more, because as you found out yourself, the lumen output decreases and the plants won't grow as fast. Cheers!

Plant dont see lumens people do! Plant see PAR as stated above with the bulb geting weaker so does
Both lummens and PAR and a bulb thats 2years old is way past its time, I would replace them every
Three flower cycles.

Thanks guys, I appreciate this. I've gone over just about everything else and this was all I could figure that was giving me my trouble.

I replace every 12 months

peace
doublejj

Every three harvests for me, the bulbs are cheap!