That's an interesting question. First, Colorado's lien enforcement deadline is a weird one. A lien must be enforced within 6 months of the date the project was completed, or labor or materials were last furnished to the project. However, there's another deadline to keep in mind - a lien claim may expire if it is not enforced within 1 year from it's filing. There's a caveat, though. If the project remains ongoing when the lien claim is approaching the 1 year-from-filing mark, an extension can be filed via affidavit with the county under § 38-22-109(8) of the Colorado lien statute. This affidavit must be filed within 1 year and 30 days of filing the lien, and it must state that the project is ongoing.
When such an extension is not filed, or if the time to enforce a filed lien passes for any other reason, a claimant will not likely be able to simply file another lien after the deadline to enforce passes - but it could potentially be possible if the deadline to file a lien has not yet passed. However, the deadline to file a lien will typically be within 2 or 4 months from last furnishing (though potentially, this deadline may be extended as well). If there is still time to file another mechanics lien, though, another notice of intent to lien would likely need to be sent prior to filing.