JS or POST trunc is the best bet, but an alternate failproof method is at the DB. You can limit it in DB by changing the cell structure to varchar(65) which would only allow 65 characters to be stored there. In phpMyAdmin you find the table, click it, then look for the "structure" tab. Find the col you wanna limit, pick varchar from dropdown, then set it to 65. This will also trunc all existing titles to 65.
EDIT: This script may be helpful too if you just wanna count the chars instead and leave it to your editors to keep it around 65. This would work on any field, just change the
input[name=""] to whatever field you need counted:
var count_name = $('input[name="MY-TITLE-INPUT-NAME"]');
var count_name_val = $(count_name).val().length;
var stage_65 = '<br/><div style="font-style:italic;"> Using <span class="stage_65">' + count_name_val + '</span> of 65 Google Chars</div>';