The Ordnung
Amish faith and life is governed by a (largely unwritten) set of rules known as the Ordnung (order). Since the Amish lack the central governing authority present in the many other Christian sects, all governance is local, as is the Ordnung.
The Amish believe in literal interpretation of the Bible. The Ordnung is designed to ensure that all members of the church live life according to the scriptures. A member of the Amish Church must live a simple life devoted to God, family and community, in accordance with God's laws. Electricity, automobiles, television, clothing fashions and the like are considered to be distractions that promote pride, envy, vanity, sloth, dishonesty and other undesirable traits.
The mode of dress, the buggy and the lantern have become the identifying marks of the Amish and are not likely to change. The mode of dress emphasizes that the Amish person is separate from the non-Amish world, but also part of a community of equals. The buggy likewise promotes equality and limits travel, keeping communities together. The lantern, a non-electric light, does not require connections outside of the community.
The Amish are not really "stuck in time." Although home and social life has remained essentially unchanged, new technologies that have passed a rigorous examination have been accepted. The Ordnung is applied to any proposed use of new technology. A technology may be accepted for business or practical reasons, but never for indulgence, desire or entertainment. A technology is more likely to be accepted if it is a natural extension of an existing technology and will have a minimal social impact. Using a nylon rope in place of a hemp rope would be an example of a natural extension. A technology is likely to be rejected if it is radically different or could have social implications. Listening to a portable stereo while doing chores would be considered a needless distraction. Any technology that is seen as degrading family or spiritual life is rejected out of hand. Television is definitely out as it brings questionable values into the home.
Now, how would the Ordnung affect the purchase of something like a stove? If an Amish buyer wished to burn wood, he could buy any wood stove. It is not necessary that the stove be an antique or even a reproduction. A modern, efficient, airtight stove would not only be acceptable, but the improved economy would make a modern stove a thrifty choice.

Freedom of Choice
It would seem that growing up Amish would be very restrictive and would not allow for any choices. On the one hand, the Ordnung is quite involved and it takes a long time for a child to learn and understand the details. On the other hand, as with Anabaptists, personal choice is important.
Baptism marks entry into the Amish church. Joining the church is a decision that cannot be made before the age of 16. By this time, a candidate will have been thoroughly drilled in the faith and the Ordnung through school and church attendance. In accord with the philosophy of choice, 16 year olds may leave the community to experience life outside if they so choose .
Any member is free to leave. A member who has left may even be allowed to return within a short time. A member who leaves permanently will, however, be shunned. Shunning means that the person will forever be considered an outsider -- a stranger -- and will not be allowed to participate in the community ever again. All family ties cease to exist. A member may also be shunned if he persistently defies the authority of the Ordnung. It is rare for a member of an Amish community to take this irreversible step.

People who join the church and then leave face the prospect of shunning, so the decision to join is not to be taken lightly. Once Amish teens turn 16 and before they become church members, they can venture out into the world. During this time -- termed Rumspringa, or "running around" -- the Amish teens live amongst "the English" and are free to behave as they choose, even if that means indulging in such non-Amish things as dancing, drugs and television.
If they choose to return and join the church, they do so with full knowledge of what they are giving up in order to be part of the community. If they do not return, family ties are still viable because they did not break an oath to the church.
The vast majority do return.