The character I am wanting this for is my Neutral Good druid who believes the best way to protect nature is to live as long as it lives. They only ways I have found are evil such as becoming a Lich or deity related.
The problem being in the world I am playing in all the deities have fallen and become mortal. Is there any way to become immortal, whether it's officially D&D or tried, tested, and backed-by-experience homebrew, without resorting to lichdom or deities?
This link to an old handbook on immortality, as well as its updated and ported version contain a fairly exhaustive list methods to gain immortality and pseudo-immortality, as well as their shortcomings and pitfalls. You may find what suits your purpose there.
Elan (SRD, Expanded Psionics Handbook), warforged (Eberron Campaign Setting) and killoren (Races of the Wild) are each timeless; though each ages through age categories, none has a maximum age. Being forest creatures, as well as fey, the killoren might suit your druidic purpose exactly.
A good way if your looking to end your campaign but leave your character for future use is to have a trusted wizard clone you or if your ify on the clone thing you could ask to have sequester cast on you wich puts you in stasis until a set event ocures so you could have him have the set event be when the treees or forest creatures sense a disturbance in nature
