Can an extension of an ARC be anticipated for more than 30 days?

Yes, you can, but you lose the time pattern of revisions. 

AMC M.A.901(c)2, (e)2 and (f): 

It is acceptable to anticipate the extension of the ARC for a maximum of 30 days without loss of the temporary standard of revisions of the certificate of airworthiness, which means that the new expiry date would be set one year after the previous expiry date. 

In case the ARC extension is anticipated more than 30 days, the continuity of the temporary airworthiness review pattern would be lost, the next expiration date being one year after the extension date. 

ML.A.901(d): 

[...] the extension of the airworthiness review certificate may be anticipated for a maximum period of 30 days without loss of continuity of the airworthiness review pattern, so that the aircraft is available for the purpose of placing the original airworthiness review certificate on board.