Does archer experience have an effect on accuracy?

[Ars Moriendi]

Merging depleted units loses some experience if not the same level(like mine).

Experience is never lost. It is tracked on an individual soldier basis, the display only showing the average for the unit.
Eg. if you merge 40 peasants at 8xp with 40 peasants at 0xp, the resulting unit will have 1 silver, but you'll still have the same number of master pitchfork ninjas.

About the original question, here's something posted half a year ago (and referenced in the FAQ):

I did a quick test on retinue longbowmen V Scottish pikemen and checked the casualties inflicted after 5 full volleys from the longbowmen.The longbows were deployed in a wide line 2 men deep directly opposite the Scots Pikemen and were left on fire at will with no other action from me.

Retinues with no experience after five full volleys - 29 casualties inflicted.

Retinues with 3 gold chevrons under the same conditions - 61 casualties inflicted.

Even though this simple test is hardly under laboratory conditions it clearly shows that there are other forces at work with the additional experience other than the missile attack rating.

There's a lot more info on this in this forum, do some searching.