Lucy gets very nostalgic and sad about leaving the apartment that she has lived in for "15 years" but she and Ricky only moved into this apartment 4 years ago (S2 E 26).
When Lucy and Ethel are reminiscing about some of the crazy things that happened in the apartment, Ethel mentions the time Lucy wallpapered her into the closet. This was from the season 2 episode "Redecorating" which actually took place in the Ricardo's old apartment.
When Lucy drags the coffee table the new tenants wanted to paint black into the Mertzes' apartment, it was not the same table. In the Ricardos' apartment it was below knee height, but the one she dragged was nearly as high as her hip. The legs were also different. The only parts the same were the drop-leaf sides.
When we see Lucy get out of bed and pace at 4am there is a smoldering cigarette in the bedroom table ashtray but no one was awake to have light it.