Hello,
I have several models of mikrotik routers and I am using them as pppoe clients for several isp in Italy.
With most of them I have the same problem (tried latest firmware):
pppoe client is always up but after some months it stops receiving packets, it only sends them.
The only thing do to is disable/enable pppoe and it restarts.
It is difficult to do an automatic script or do a failover because the pppoe connection stays up so it keeps default route and so on.
I know that with months time to failure it is hard to analyse, but have you sniffed the traffic on the underlying physical interface of bridge of the PPPoE into a file when the connection was in this state and could you see using Wireshark the PPPoE “transport” packets coming from the ISP in that file? I.e. are you sure that the issue is really that the PPPoE client of Mikrotik is not unpacking the contents from the transport packets and not the fact that the ISP stops sending them?
Unfortunately, my only PPPoE client gets restarted for “natural” reasons much more often than once in several months so I have no data to compare.
The fact that several ISPs exhibit the same behaviour has little relevance unless you are bullet-proof that they use different technology.